code: def cql_encode_map_collection(self, val):
          
          return '{%s}' % ', '.join('%s: %s' % (
              self.mapping.get(type(k), self.cql_encode_object)(k),
              self.mapping.get(type(v), self.cql_encode_object)(v)
          ) for k, v in six.iteritems(val))
docs: Converts a dict into a string of the form ``{key1: val1, key2: val2, ...}``.
          This is suitable for ``map`` type columns.