parameters: (self)
docstring: Return a count of messages in the mailbox.
docstring_summary: Return a count of messages in the mailbox.
docstring_tokens: Return a count of messages in the mailbox .
function: def __len__(self):
          """Return a count of messages in the mailbox."""
          raise NotImplementedError('Method must be implemented by subclass')
function_tokens: def __len__ ( self ) : raise NotImplementedError ( 'Method must be implemented by subclass' )