def xhdr(self, header, msgid_range=None):
args = header<EOL>if range is not None:<EOL><INDENT>args += "<STR_LIT:U+0020>" + utils.unparse_msgid_range(msgid_range)<EOL><DEDENT>code, message = self.command("<STR_LIT>", args)<EOL>if code != <NUM_LIT>:<EOL><INDENT>raise NNTPReplyError(code, message)<EOL><DEDENT>return self.info(code, message)<EOL>
XHDR command.