docs: def merge_schemas(cls, schema, _schema):
          """Return second Schema, which is extended by first Schema
          https://github.com/OAI/OpenAPI-Specification/blob/master/versions/2.0.md#composition-and-inheritance-polymorphism
          """
          tmp = schema.properties[:]  # copy
          prop = {}
          to_dict = lambda e: prop.update({e.pop('name'): e})
          [to_dict(i) for i in tmp]  # map(to_dict, tmp)
          for _prop in _schema.properties:
              if prop.get(_prop['name']):
                  prop.pop(_prop['name'])
          if prop:
              for k, v in prop.items():
                  v['name'] = k
                  _schema.properties.append(v)
          return _schema