code: def get_subtask_fields(config_class):
      
      from lsst.pex.config import ConfigurableField, RegistryField
  
      def is_subtask_field(obj):
          return isinstance(obj, (ConfigurableField, RegistryField))
  
      return _get_alphabetical_members(config_class, is_subtask_field)
docs: Get all configurable subtask fields from a Config class.
  
      Parameters
      ----------
      config_class : ``lsst.pipe.base.Config``-type
          The configuration class (not an instance) corresponding to a Task.
  
      Returns
      -------
      subtask_fields : `dict`
          Mapping where keys are the config attribute names and values are
          subclasses of ``lsst.pex.config.ConfigurableField`` or
          ``RegistryField``). The mapping is alphabetically ordered by
          attribute name.