docs: def __filter(filterable, filter_, logic_operation='and'):
          """ filtering DataFrame using filter_ key-value conditions applying logic_operation
          only find rows strictly fitting the filter_ criterion"""
          condition = []
          if not filter_:
              return filterable
          elif filter_.get('type') == '__ANY__':
              return filterable
          else:
              for key, value in filter_.items():
                  condition.append('{key} == "{value}"'.format(key=key, value=value))
          try:
              res = filterable.query(" {operation} ".format(operation=logic_operation).join(condition))
          except pd.core.computation.ops.UndefinedVariableError:
              return pd.DataFrame()
          else:
              return res