code: def main_pred_type(self, value):
          
          if value not in operators:
              value = operator_lkup.get(value)
          if value:
              self._main_pred_type = value
              self.payload['predicate']['type'] = self._main_pred_type
          else:
              raise Exception("main predicate combiner not a valid operator")
docs: set main predicate combination type
  
          :param value: (character) One of ``equals`` (``=``), ``and`` (``&``), ``or`` (``|``),
          ``lessThan`` (``<``), ``lessThanOrEquals`` (``<=``), ``greaterThan`` (``>``),
          ``greaterThanOrEquals`` (``>=``), ``in``, ``within``, ``not`` (``!``), ``like``