How to use the rwslib.builders.metadata.MeasurementUnitRef function in rwslib

"""Override << operator"""

        # ExternalQuestion?,,
        # Role*, Alias*,
        # mdsol:HelpText?, mdsol:ViewRestriction* or mdsolEntryRestrictions*), (or mdsol:ReviewGroups*), mdsol:Label?)

        if not isinstance(other, (MdsolHelpText, MdsolEntryRestriction, MdsolViewRestriction, Question,
                                  MeasurementUnitRef, CodeListRef, MdsolHeaderText, MdsolReviewGroup, RangeCheck,
                                  Alias,)):
            raise ValueError('ItemDef cannot accept a {0} as a child element'.format(other.__class__.__name__))

        self.set_single_attribute(other, Question, 'question')
        self.set_single_attribute(other, CodeListRef, 'codelistref')
        self.set_single_attribute(other, MdsolHeaderText, 'header_text')
        self.set_list_attribute(other, RangeCheck, 'range_checks')
        self.set_list_attribute(other, MeasurementUnitRef, 'measurement_unit_refs')
        self.set_list_attribute(other, MdsolHelpText, 'help_texts')
        self.set_list_attribute(other, MdsolViewRestriction, 'view_restrictions')
        self.set_list_attribute(other, MdsolEntryRestriction, 'entry_restrictions')
        self.set_list_attribute(other, MdsolReviewGroup, 'review_groups')
        self.set_list_attribute(other, Alias, 'aliases')
        return other

def __lshift__(self, other):
        if not isinstance(other, (MeasurementUnitRef, AuditRecord, MdsolQuery, Annotation,
                                  MdsolProtocolDeviation)):
            raise ValueError("ItemData object can only receive MeasurementUnitRef, AuditRecord, Annotation,"
                             "MdsolProtocolDeviation or MdsolQuery objects")
        self.set_single_attribute(other, MeasurementUnitRef, 'measurement_unit_ref')
        self.set_single_attribute(other, AuditRecord, 'audit_record')
        self.set_list_attribute(other, MdsolQuery, 'queries')
        self.set_list_attribute(other, MdsolProtocolDeviation, 'deviations')
        self.set_list_attribute(other, Annotation, 'annotations')
        return other

def __lshift__(self, other):
        """Override << operator"""

        # ExternalQuestion?,,
        # Role*, Alias*,
        # mdsol:HelpText?, mdsol:ViewRestriction* or mdsolEntryRestrictions*), (or mdsol:ReviewGroups*), mdsol:Label?)

        if not isinstance(other, (MdsolHelpText, MdsolEntryRestriction, MdsolViewRestriction, Question,
                                  MeasurementUnitRef, CodeListRef, MdsolHeaderText, MdsolReviewGroup, RangeCheck,
                                  Alias,)):
            raise ValueError('ItemDef cannot accept a {0} as a child element'.format(other.__class__.__name__))

        self.set_single_attribute(other, Question, 'question')
        self.set_single_attribute(other, CodeListRef, 'codelistref')
        self.set_single_attribute(other, MdsolHeaderText, 'header_text')
        self.set_list_attribute(other, RangeCheck, 'range_checks')
        self.set_list_attribute(other, MeasurementUnitRef, 'measurement_unit_refs')
        self.set_list_attribute(other, MdsolHelpText, 'help_texts')
        self.set_list_attribute(other, MdsolViewRestriction, 'view_restrictions')
        self.set_list_attribute(other, MdsolEntryRestriction, 'entry_restrictions')
        self.set_list_attribute(other, MdsolReviewGroup, 'review_groups')
        self.set_list_attribute(other, Alias, 'aliases')
        return other

def __lshift__(self, other):
        """Override << operator"""
        if not isinstance(other, (CheckValue, MeasurementUnitRef,)):
            raise ValueError('RangeCheck cannot accept a {0} as a child element'.format(other.__class__.__name__))

        self.set_single_attribute(other, CheckValue, 'check_value')
        self.set_single_attribute(other, MeasurementUnitRef, 'measurement_unit_ref')

def __lshift__(self, other):
        if not isinstance(other, (MeasurementUnitRef, AuditRecord, MdsolQuery, Annotation,
                                  MdsolProtocolDeviation)):
            raise ValueError("ItemData object can only receive MeasurementUnitRef, AuditRecord, Annotation,"
                             "MdsolProtocolDeviation or MdsolQuery objects")
        self.set_single_attribute(other, MeasurementUnitRef, 'measurement_unit_ref')
        self.set_single_attribute(other, AuditRecord, 'audit_record')
        self.set_list_attribute(other, MdsolQuery, 'queries')
        self.set_list_attribute(other, MdsolProtocolDeviation, 'deviations')
        self.set_list_attribute(other, Annotation, 'annotations')
        return other