def is_error_transition_for?(event_name, error)
      is_same_event?(event_name) && from.is_a?(Class) && error.is_a?(from)
    end
def is_error_transition_for?(event_name, error)
      is_same_event?(event_name) && from.is_a?(Class) && error.is_a?(from)
    end
returns true if it's a error transition for event_name and error