code: def add_predicate(self, key, value, predicate_type='equals'):
          
          if predicate_type not in operators:
              predicate_type = operator_lkup.get(predicate_type)
          if predicate_type:
              self.predicates.append({'type': predicate_type,
                                      'key': key,
                                      'value': value
                                      })
          else:
              raise Exception("predicate type not a valid operator")
docs: add key, value, type combination of a predicate
  
          :param key: query KEY parameter
          :param value: the value used in the predicate
          :param predicate_type: the type of predicate (e.g. ``equals``)