'Return a useful multiline rep of self'

def dump(self):

    header = ('Addressee:    %s\nLength:    %s\nSent    %s' % (self.address, len(self.text), self.sent_ts))
    csm_info = ''
    if self.is_csm:
        csm_info = ('\nCSM:    %d    of    %d    for    Ref#    %d' % (self.csm_seq, self.csm_total, self.csm_ref))
    return ('%s%s\nMessage:    \n%s\nPDU:    %s' % (header, csm_info, self.text, self.pdu_string))
