'(typ, [data, ...]) = partial(message_num, message_part, start, length)
Fetch truncated part of a message.
\'data\' is tuple of message part envelope and data.
NB: obsolete.'

def partial(self, message_num, message_part, start, length, **kw):

    name = 'PARTIAL'
    kw['untagged_response'] = 'FETCH'
    return self._simple_command(name, message_num, message_part, start, length, **kw)
