How to use the pythoms.psims.CVParameterSet function in pythoms

"""
    Interprets an xml branch as CVParams

    :param branch:
    :return: controlled value parameter set with values
    :rtype: CVParameterSet
    """
    out = {}
    for cvParam in branch.getElementsByTagName('cvParam'):
        acc = cvParam.getAttribute('accession')  # accession key
        out[acc] = {}
        for attribute, value in cvParam.attributes.items():  # pull all the attributes
            if attribute != 'accession':
                # attempt to convert to integer or float, keep as string otherwise
                out[acc][attribute] = stringtodigit(value)
    return CVParameterSet(**out)

'UO:0000098': 'milliliter',
    'UO:0000106': 'hertz',
    'UO:0000110': 'pascal',
    'UO:0000112': 'joule',
    'UO:0000166': 'parts per notation unit',
    'UO:0000169': 'parts per million',
    'UO:0000175': 'gram per liter',
    'UO:0000185': 'degree',
    'UO:0000218': 'volt',
    'UO:0000228': 'tesla',
    'UO:0000266': 'electronvolt',
    'UO:0000268': 'volt per meter',
}

# object for automatic retrieval of unit names from accession values
cv_units = CVParameterSet(
    **{acc: {'name': unit_definitions[acc]} for acc in unit_definitions}
)

'MS:1000580': 'MSn spectrum',
        'MS:1000581': 'CRM spectrum',
        'MS:1000582': 'SIM spectrum',
        'MS:1000583': 'SRM spectrum',
    }
    othertypes = {  # other accession keys (non-MS)
        'MS:1000620': 'PDA spectrum',
        'MS:1000804': 'electromagnetic radiation spectrum',
        'MS:1000805': 'emission spectrum',
        'MS:1000806': 'absorption spectrum',
    }
    out = {}
    if isinstance(hand, CVParameterSet):  # handed a cvparam class object (expected)
        p = hand
    else:  # handed a tree or branch (generate the cvparam class object)
        p = CVParameterSet(hand)
    for acc in p.keys() & mstypes.keys():  # check for ms spectrum
        out['acc'] = acc  # accession code
        out['name'] = mstypes[acc]  # name of spectrum
        out['type'] = 'MS'  # it is a mass spectrum
        out['level'] = p['MS:1000511'].value  # ms level
        out['window'] = [p['MS:1000501'].value, p['MS:1000500'].value]  # scan window
        if 'MS:1000129' in p:  # negative scan
            out['mode'] = '-'
        elif 'MS:1000130' in p:  # positive scan
            out['mode'] = '+'
        if 'MS:1000827' in p:  # if there is an isolation window target m/z
            out['target'] = p['MS:1000827'].value
        # if MSn > 2, not sure how to handle this (will have to be hard coded later as I have no examples)
        elif out['level'] > 2:
            raise ValueError(
                'This script has not been coded to handle MSn > 2, please contact the author of the class')

'MS:1000341': 'precursor ion spectrum',
        'MS:1000343': 'product ion spectrum',
        'MS:1000579': 'MS1 spectrum',
        'MS:1000580': 'MSn spectrum',
        'MS:1000581': 'CRM spectrum',
        'MS:1000582': 'SIM spectrum',
        'MS:1000583': 'SRM spectrum',
    }
    othertypes = {  # other accession keys (non-MS)
        'MS:1000620': 'PDA spectrum',
        'MS:1000804': 'electromagnetic radiation spectrum',
        'MS:1000805': 'emission spectrum',
        'MS:1000806': 'absorption spectrum',
    }
    out = {}
    if isinstance(hand, CVParameterSet):  # handed a cvparam class object (expected)
        p = hand
    else:  # handed a tree or branch (generate the cvparam class object)
        p = CVParameterSet(hand)
    for acc in p.keys() & mstypes.keys():  # check for ms spectrum
        out['acc'] = acc  # accession code
        out['name'] = mstypes[acc]  # name of spectrum
        out['type'] = 'MS'  # it is a mass spectrum
        out['level'] = p['MS:1000511'].value  # ms level
        out['window'] = [p['MS:1000501'].value, p['MS:1000500'].value]  # scan window
        if 'MS:1000129' in p:  # negative scan
            out['mode'] = '-'
        elif 'MS:1000130' in p:  # positive scan
            out['mode'] = '+'
        if 'MS:1000827' in p:  # if there is an isolation window target m/z
            out['target'] = p['MS:1000827'].value
        # if MSn > 2, not sure how to handle this (will have to be hard coded later as I have no examples)

:rtype: str
        """
        name = name.lower()  # avoids case sensitivity
        for acc in self.cv_values:
            if self.cv_values[acc].name.lower() == name:
                return acc
        raise KeyError(f'No accession key was found matching the supplied name {name}.')

    def print_properties(self, key):
        """Prints the properties of the provided key"""
        cv_param_def.print_properties(key)  # print the detailed information
        if self.cv_values[key].value is not None:
            print(f'value: {self.cv_values[key].value}')  # followed by the value


class CVParameterDefinitions(CVParameterSet):
    def __init__(self,
                 obo_path=OBOURL,
                 ):
        """
        Loads and interprets a PSI-MS obo file into a python-interpretable format.

        :param obo_path: file path or url to an obo file
        """
        CVParameterSet.__init__(self)
        try:
            self.obo_file = obonet.read_obo(obo_path)  # read the obo file
        except (FileNotFoundError, urllib.error.HTTPError):
            raise FileNotFoundError(f'An obo file could not be found at the provided path or URL: {obo_path}')
        if obo_path == OBOURL:  # remind the user to cite the pulication
            print('Data was read from PSI-MS, please cite DOI: 10.1093/database/bat009')
        self.format_version = self.obo_file.graph['format-version']

def __init__(self,
                 obo_path=OBOURL,
                 ):
        """
        Loads and interprets a PSI-MS obo file into a python-interpretable format.

        :param obo_path: file path or url to an obo file
        """
        CVParameterSet.__init__(self)
        try:
            self.obo_file = obonet.read_obo(obo_path)  # read the obo file
        except (FileNotFoundError, urllib.error.HTTPError):
            raise FileNotFoundError(f'An obo file could not be found at the provided path or URL: {obo_path}')
        if obo_path == OBOURL:  # remind the user to cite the pulication
            print('Data was read from PSI-MS, please cite DOI: 10.1093/database/bat009')
        self.format_version = self.obo_file.graph['format-version']
        self.data_version = self.obo_file.graph['data-version']
        for acc in self.obo_file:
            dct = self.obo_file.nodes[acc]
            if 'def' in dct:  # if the invalid key def is in the dictionary, convert and remove
                dct['definition'] = dct['def']
                del dct['def']
            self.cv_values[acc] = CVParam(
                id=acc,
                **dct,