def get_argument_starttime(self):
try:<EOL><INDENT>starttime = self.get_argument(constants.PARAM_STARTTIME)<EOL>return starttime<EOL><DEDENT>except tornado.web.MissingArgumentError as e:<EOL><INDENT>raise Exception(e.log_message)<EOL><DEDENT>
Helper function to get starttime argument.
Raises exception if argument is missing.
Returns the starttime argument.