code: def get_vertex_field_type(current_schema_type, vertex_field_name):
      
      # According to the schema, the vertex field itself is of type GraphQLList, and this is
      # what get_field_type_from_schema returns. We care about what the type *inside* the list is,
      # i.e., the type on the other side of the edge (hence .of_type).
      # Validation guarantees that the field must exist in the schema.
      if not is_vertex_field_name(vertex_field_name):
          raise AssertionError(u'Trying to load the vertex field type of a non-vertex field: '
                               u'{} {}'.format(current_schema_type, vertex_field_name))
  
      raw_field_type = get_field_type_from_schema(current_schema_type, vertex_field_name)
      if not isinstance(strip_non_null_from_type(raw_field_type), GraphQLList):
          raise AssertionError(u'Found an edge whose schema type was not GraphQLList: '
                               u'{} {} {}'.format(current_schema_type, vertex_field_name,
                                                  raw_field_type))
      return raw_field_type.of_type
docs: Return the type of the vertex within the specified vertex field name of the given type.