<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _parse_param(key):
 """ Parse the query param looking for filters Determine the field to filter on & the operator to be used when filtering. :param key: The query parameter to the left of the equal sign :return: tuple of string field name & string operator """


    regex = re.compile(r'filter\[([A-Za-z0-9_./]+)\]')
    match = regex.match(key)

    if match:
        field_and_oper = match.groups()[0].split('__')

        if len(field_and_oper) == 1:
            return field_and_oper[0], 'eq'
        elif len(field_and_oper) == 2:
            return tuple(field_and_oper)
        else:
            raise InvalidQueryParams(**{
                'detail': 'The filter query param of "%s" is not '
                          'supported. Multiple filter operators are '
                          'not allowed in a single expression.' % key,
                'links': LINK,
                'parameter': PARAM,
            })