':param callback: see callback_method parameter in
`BlockingConnection.add_on_connection_blocked_callback` and
`BlockingConnection.add_on_connection_unblocked_callback`
:param pika.frame.Method method_frame: with method_frame.method of type
`pika.spec.Connection.Blocked` or `pika.spec.Connection.Unblocked`'

def __init__(self, callback, method_frame):

    self._callback = callback
    self._method_frame = method_frame
