How to use the stix2.properties.StringProperty function in stix2

`the STIX 2.0 specification `__.
    """

    _type = 'observed-data'
    _properties = OrderedDict([
        ('type', TypeProperty(_type)),
        ('id', IDProperty(_type, spec_version='2.0')),
        ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.0')),
        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
        ('first_observed', TimestampProperty(required=True)),
        ('last_observed', TimestampProperty(required=True)),
        ('number_observed', IntegerProperty(min=1, max=999999999, required=True)),
        ('objects', ObservableProperty(spec_version="2.0", required=True)),
        ('revoked', BooleanProperty(default=lambda: False)),
        ('labels', ListProperty(StringProperty)),
        ('external_references', ListProperty(ExternalReference)),
        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.0'))),
        ('granular_markings', ListProperty(GranularMarking)),
    ])

    def __init__(self, *args, **kwargs):
        self.__allow_custom = kwargs.get('allow_custom', False)
        self._properties['objects'].allow_custom = kwargs.get('allow_custom', False)

        super(ObservedData, self).__init__(*args, **kwargs)


class Report(STIXDomainObject):
    """For more detailed information on this object's properties, see
    `the STIX 2.0 specification `__.
    """

"system",
            ]),
        ),
    ])


class WindowsServiceExt(_Extension):
    # TODO: Add link
    """For more detailed information on this object's properties, see
    `the STIX 2.1 specification `__.
    """

    _type = 'windows-service-ext'
    _properties = OrderedDict([
        ('service_name', StringProperty()),
        ('descriptions', ListProperty(StringProperty)),
        ('display_name', StringProperty()),
        ('group_name', StringProperty()),
        (
            'start_type', EnumProperty(allowed=[
                "SERVICE_AUTO_START",
                "SERVICE_BOOT_START",
                "SERVICE_DEMAND_START",
                "SERVICE_DISABLED",
                "SERVICE_SYSTEM_ALERT",
            ]),
        ),
        ('service_dll_refs', ListProperty(ObjectReferenceProperty(valid_types='file'))),
        (
            'service_type', EnumProperty(allowed=[
                "SERVICE_KERNEL_DRIVER",
                "SERVICE_FILE_SYSTEM_DRIVER",

class Campaign(STIXDomainObject):
    """For more detailed information on this object's properties, see
    `the STIX 2.0 specification `__.
    """

    _type = 'campaign'
    _properties = OrderedDict([
        ('type', TypeProperty(_type)),
        ('id', IDProperty(_type, spec_version='2.0')),
        ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.0')),
        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
        ('name', StringProperty(required=True)),
        ('description', StringProperty()),
        ('aliases', ListProperty(StringProperty)),
        ('first_seen', TimestampProperty()),
        ('last_seen', TimestampProperty()),
        ('objective', StringProperty()),
        ('revoked', BooleanProperty(default=lambda: False)),
        ('labels', ListProperty(StringProperty)),
        ('external_references', ListProperty(ExternalReference)),
        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.0'))),
        ('granular_markings', ListProperty(GranularMarking)),
    ])


class CourseOfAction(STIXDomainObject):
    """For more detailed information on this object's properties, see
    `the STIX 2.0 specification `__.
    """

if type(value) in OBJ_MAP_MARKING.values():
            return value
        else:
            raise ValueError("must be a Statement, TLP Marking or a registered marking.")


class MarkingDefinition(_STIXBase, _MarkingsMixin):
    # TODO: Add link
    """For more detailed information on this object's properties, see
    `the STIX 2.1 specification `__.
    """

    _type = 'marking-definition'
    _properties = OrderedDict([
        ('type', TypeProperty(_type)),
        ('spec_version', StringProperty(fixed='2.1')),
        ('id', IDProperty(_type)),
        ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
        ('external_references', ListProperty(ExternalReference)),
        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
        ('granular_markings', ListProperty(GranularMarking)),
        ('definition_type', StringProperty(required=True)),
        ('definition', MarkingProperty(required=True)),
    ])

    def __init__(self, **kwargs):
        if set(('definition_type', 'definition')).issubset(kwargs.keys()):
            # Create correct marking type object
            try:
                marking_type = OBJ_MAP_MARKING[kwargs['definition_type']]
            except KeyError:

_type = 'language-content'
    _properties = OrderedDict([
        ('type', TypeProperty(_type)),
        ('spec_version', StringProperty(fixed='2.1')),
        ('id', IDProperty(_type, spec_version='2.1')),
        ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
        ('object_ref', ReferenceProperty(valid_types=["SCO", "SDO", "SRO"], spec_version='2.1', required=True)),
        # TODO: 'object_modified' it MUST be an exact match for the modified time of the STIX Object (SRO or SDO) being referenced.
        ('object_modified', TimestampProperty(precision='millisecond')),
        # TODO: 'contents' https://docs.google.com/document/d/1ShNq4c3e1CkfANmD9O--mdZ5H0O_GLnjN28a_yrEaco/edit#heading=h.cfz5hcantmvx
        ('contents', DictionaryProperty(spec_version='2.1', required=True)),
        ('revoked', BooleanProperty()),
        ('labels', ListProperty(StringProperty)),
        ('confidence', IntegerProperty()),
        ('external_references', ListProperty(ExternalReference)),
        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
        ('granular_markings', ListProperty(GranularMarking)),
    ])


class TLPMarking(_STIXBase):
    # TODO: Add link
    """For more detailed information on this object's properties, see
    `the STIX 2.1 specification `__.
    """

    _type = 'tlp'
    _properties = OrderedDict([
        ('tlp', StringProperty(required=True)),

('external_id', StringProperty()),
    ])

    def _check_object_constraints(self):
        super(ExternalReference, self)._check_object_constraints()
        self._check_at_least_one_property(['description', 'external_id', 'url'])


class KillChainPhase(_STIXBase):
    # TODO: Add link
    """For more detailed information on this object's properties, see
    `the STIX 2.1 specification `__.
    """

    _properties = OrderedDict([
        ('kill_chain_name', StringProperty(required=True)),
        ('phase_name', StringProperty(required=True)),
    ])


class GranularMarking(_STIXBase):
    # TODO: Add link
    """For more detailed information on this object's properties, see
    `the STIX 2.1 specification `__.
    """

    _properties = OrderedDict([
        ('lang', StringProperty()),
        ('marking_ref', ReferenceProperty(valid_types='marking-definition', spec_version='2.1')),
        ('selectors', ListProperty(SelectorProperty, required=True)),
    ])

else:
                if 'windows-process-ext' in self.get('extensions', {}):
                    self.extensions['windows-process-ext']._check_at_least_one_property()


class Software(_Observable):
    # TODO: Add link
    """For more detailed information on this object's properties, see
    `the STIX 2.1 specification `__.
    """

    _type = 'software'
    _properties = OrderedDict([
        ('type', TypeProperty(_type)),
        ('id', IDProperty(_type, spec_version='2.1')),
        ('name', StringProperty(required=True)),
        ('cpe', StringProperty()),
        ('languages', ListProperty(StringProperty)),
        ('vendor', StringProperty()),
        ('version', StringProperty()),
        ('extensions', ExtensionsProperty(spec_version='2.1', enclosing_type=_type)),
        ('spec_version', StringProperty(fixed='2.1')),
        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
        ('granular_markings', ListProperty(GranularMarking)),
        ('defanged', BooleanProperty(default=lambda: False)),
    ])
    _id_contributing_properties = ["name", "cpe", "vendor", "version"]


class URL(_Observable):
    # TODO: Add link
    """For more detailed information on this object's properties, see

class Identity(STIXDomainObject):
    """For more detailed information on this object's properties, see
    `the STIX 2.0 specification `__.
    """

    _type = 'identity'
    _properties = OrderedDict([
        ('type', TypeProperty(_type)),
        ('id', IDProperty(_type, spec_version='2.0')),
        ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.0')),
        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
        ('name', StringProperty(required=True)),
        ('description', StringProperty()),
        ('identity_class', StringProperty(required=True)),
        ('sectors', ListProperty(StringProperty)),
        ('contact_information', StringProperty()),
        ('revoked', BooleanProperty(default=lambda: False)),
        ('labels', ListProperty(StringProperty)),
        ('external_references', ListProperty(ExternalReference)),
        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.0'))),
        ('granular_markings', ListProperty(GranularMarking)),
    ])


class Indicator(STIXDomainObject):
    """For more detailed information on this object's properties, see
    `the STIX 2.0 specification `__.
    """

    _type = 'indicator'

('type', TypeProperty(_type)),
        ('spec_version', StringProperty(fixed='2.1')),
        ('id', IDProperty(_type, spec_version='2.1')),
        ('created_by_ref', ReferenceProperty(valid_types='identity', spec_version='2.1')),
        ('created', TimestampProperty(default=lambda: NOW, precision='millisecond')),
        ('modified', TimestampProperty(default=lambda: NOW, precision='millisecond')),
        ('description', StringProperty()),
        ('first_seen', TimestampProperty()),
        ('last_seen', TimestampProperty()),
        ('count', IntegerProperty(min=0, max=999999999)),
        ('sighting_of_ref', ReferenceProperty(valid_types="SDO", spec_version='2.1', required=True)),
        ('observed_data_refs', ListProperty(ReferenceProperty(valid_types='observed-data', spec_version='2.1'))),
        ('where_sighted_refs', ListProperty(ReferenceProperty(valid_types='identity', spec_version='2.1'))),
        ('summary', BooleanProperty()),
        ('revoked', BooleanProperty(default=lambda: False)),
        ('labels', ListProperty(StringProperty)),
        ('confidence', IntegerProperty()),
        ('lang', StringProperty()),
        ('external_references', ListProperty(ExternalReference)),
        ('object_marking_refs', ListProperty(ReferenceProperty(valid_types='marking-definition', spec_version='2.1'))),
        ('granular_markings', ListProperty(GranularMarking)),
    ])

    # Explicitly define the first kwargs to make readable Sighting declarations.
    def __init__(self, sighting_of_ref=None, **kwargs):
        # Allow sighting_of_ref as a positional arg.
        if sighting_of_ref and not kwargs.get('sighting_of_ref'):
            kwargs['sighting_of_ref'] = sighting_of_ref

        super(Sighting, self).__init__(**kwargs)

    def _check_object_constraints(self):

('external_id', StringProperty()),
    ])

    def _check_object_constraints(self):
        super(ExternalReference, self)._check_object_constraints()
        self._check_at_least_one_property(['description', 'external_id', 'url'])


class KillChainPhase(_STIXBase):
    """For more detailed information on this object's properties, see
    `the STIX 2.0 specification `__.
    """

    _properties = OrderedDict([
        ('kill_chain_name', StringProperty(required=True)),
        ('phase_name', StringProperty(required=True)),
    ])


class GranularMarking(_STIXBase):
    """For more detailed information on this object's properties, see
    `the STIX 2.0 specification `__.
    """

    _properties = OrderedDict([
        ('marking_ref', ReferenceProperty(required=True, type='marking-definition')),
        ('selectors', ListProperty(SelectorProperty, required=True)),
    ])


class TLPMarking(_STIXBase):
    """For more detailed information on this object's properties, see