docs: def execute(self, data_dict, callback, group=None, trace=None):
          """Low level method to expand the template piece by piece.
  
      Args:
        data_dict: The JSON data dictionary.
        callback: A callback which should be called with each expanded token.
        group: Dictionary of name -> Template instance (for styles)
  
      Example: You can pass 'f.write' as the callback to write directly to a file
      handle.
      """
          # First try the passed in version, then the one set by _SetTemplateGroup.  May
          # be None.  Only one of these should be set.
          group = group or self.group
          context = _ScopedContext(data_dict, self.undefined_str, group=group)
          _Execute(self._program.Statements(), context, callback, trace)