'Handle a TOP command.
@type i: L{bytes}
@param i: A 1-based message index.
@type size: L{bytes}
@param size: The number of lines of the message to retrieve.
@rtype: L{Deferred}
@return: A deferred which triggers after the response to the TOP
command has been issued.'

def do_TOP(self, i, size):

    try:
        size = int(size)
        if (size < 0):
            raise ValueError
    except ValueError:
        self.failResponse('Bad    line    count    argument')
    else:
        return self._sendMessageContent(i, (lambda fp: _HeadersPlusNLines(fp, size)), (lambda size: 'Top    of    message    follows'))
