old_contents: # coding=utf-8
  
  
  class EFBException(Exception):
      """A general class to indicate that the exception is from EFB framework."""
      pass
  
  
  class EFBChatNotFound(EFBException):
      """
      Raised by a slave channel when a chat indicated is not found.
  
      Can be raised by any method that involves a chat or a message.
      """
      pass
  
  
  class EFBChannelNotFound(EFBException):
      """
      Raised by the coordinator when the message sent delivers to
      a missing channel.
      """
      pass
  
  
  class EFBMessageError(EFBException):
      """
      Raised by slave channel for any other error occurred when sending
      a message or a status.
  
      Can be raised in :meth:`.EFBChannel.send_message` and :meth:`.EFBChannel.send_status`.
      """
      pass
  
  
  class EFBMessageNotFound(EFBMessageError):
      """
      Raised by a slave channel when a message indicated is not found.
  
      Can be raised in :meth:`.EFBChannel.send_message` (edited message / target message not found)
      and in :meth:`.EFBChannel.send_status` (message to delete is not found).
      """
      pass
  
  
  class EFBMessageTypeNotSupported(EFBMessageError):
      """
      Raised by a slave channel when the indicated message type is not supported.
  
      Can be raised in :meth:`.EFBChannel.send_message`.
      """
      pass
  
  
  class EFBOperationNotSupported(EFBMessageError):
      """
      Raised by slave channels when a chat operation is not supported.
      E.g.: cannot edit message, cannot delete message.
  
      Can be raised in :meth:`.EFBChannel.send_message` and :meth:`.EFBChannel.send_status`.
      """
      pass
  
new_contents: # coding=utf-8
  
  
  class EFBException(Exception):
      """A general class to indicate that the exception is from EFB framework."""
      pass
  
  
  class EFBChatNotFound(EFBException):
      """
      Raised by a slave channel when a chat indicated is not found.
  
      Can be raised by any method that involves a chat or a message.
      """
      pass
  
  
  class EFBChannelNotFound(EFBException):
      """
      Raised by the coordinator when the message sent delivers to
      a missing channel.
      """
      pass
  
  
  class EFBMessageError(EFBException):
      """
      Raised by slave channel for any other error occurred when sending
      a message or a status.
  
      Can be raised in :meth:`.EFBChannel.send_message` and :meth:`.EFBChannel.send_status`.
      """
      pass
  
  
  class EFBMessageNotFound(EFBMessageError):
      """
      Raised by a slave channel when a message indicated is not found.
  
      Can be raised in :meth:`.EFBChannel.send_message` (edited message / target message not found)
      and in :meth:`.EFBChannel.send_status` (message to delete is not found).
      """
      pass
  
  
  class EFBMessageTypeNotSupported(EFBMessageError):
      """
      Raised by a slave channel when the indicated message type is not supported.
  
      Can be raised in :meth:`.EFBChannel.send_message`.
      """
      pass
  
  
  class EFBOperationNotSupported(EFBMessageError):
      """
      Raised by slave channels when a chat operation is not supported.
      E.g.: cannot edit message, cannot delete message.
  
      Can be raised in :meth:`.EFBChannel.send_message` and :meth:`.EFBChannel.send_status`.
      """
      pass
  
  
  class EFBMessageReactionNotPossible(EFBException):
      """
      Raised by slave channel when a message reaction request from master channel is
      not possible to be processed.
  
      Can be raised in :meth:`.EFBChannel.send_status`.
      """
      pass
  
subject: Implement #171