code: def _derive_typedef(typ):
      '''Return single, existing super type typedef or None.
      '''
      v = [v for v in _values(_typedefs) if _issubclass(typ, v.type)]
      if len(v) == 1:
          return v[0]
      return Nonf _derive_typedef(typ):
      '''Return single, existing super type typedef or None.
      '''
      v = [v for v in _values(_typedefs) if _issubclass(typ, v.type)]
      if len(v) == 1:
          return v[0]
      return None
docs: Return single, existing super type typedef or None.