parameters: (self, handler, on_error=None)
docstring: Add a child handler
  
          :param handler: A child handler
          :type handler: :class:`Handler` or one of its derivatives.
          :param on_error: Not used
docstring_summary: Add a child handler
docstring_tokens: Add a child handler
function: def add(self, handler, on_error=None):
          """
          Add a child handler
  
          :param handler: A child handler
          :type handler: :class:`Handler` or one of its derivatives.
          :param on_error: Not used
          """
          self.handlers.append(handler)
function_tokens: def add ( self , handler , on_error = None ) : self . handlers . append ( handler )