Python representation of a mzML cvParam = tuple(accession, value,
    unitAccession).

    :param attributes: #TODO: docstring

    :returns: #TODO: docstring

def cvParamFromDict(attributes):
    """Python representation of a mzML cvParam = tuple(accession, value,
    unitAccession).

    :param attributes: #TODO: docstring

    :returns: #TODO: docstring
    """
    keys = ['accession', 'value', 'unitAccession']
    return tuple(attributes[key] if key in attributes else None for key in keys)