code: def add_index(self, attribute, ordered=False):
          
          return self._encode_invoke(map_add_index_codec, attribute=attribute, ordered=ordered)
docs: Adds an index to this map for the specified entries so that queries can run faster.
  
          Example:
              Let's say your map values are Employee objects.
                  >>> class Employee(IdentifiedDataSerializable):
                  >>>     active = false
                  >>>     age = None
                  >>>     name = None
                  >>>     #other fields
                  >>>
                  >>>     #methods
  
              If you query your values mostly based on age and active fields, you should consider indexing these.
                  >>> map = self.client.get_map("employees")
                  >>> map.add_index("age" , true) #ordered, since we have ranged queries for this field
                  >>> map.add_index("active", false) #not ordered, because boolean field cannot have range
  
  
          :param attribute: (str), index attribute of the value.
          :param ordered: (bool), for ordering the index or not (optional).