code: def get_smtp_header(self):
          
          header = "From: %s\r\n" % self.get_sender()
          header += "To: %s\r\n" % ',\r\n '.join(self.get_to())
          header += "Cc: %s\r\n" % ',\r\n '.join(self.get_cc())
          header += "Bcc: %s\r\n" % ',\r\n '.join(self.get_bcc())
          header += "Subject: %s\r\n" % self.get_subject()
          return header
docs: Returns the SMTP formatted header of the line.
  
          :rtype:  string
          :return: The SMTP header.