<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_opt(self, opt, value=None):
 """Add option to job. Parameters opt : string Name of option (e.g. --output-file-format) value : string, (default=None) The value for the option (no value if set to None). """

        if value is None:
            self.common_options += [opt]
        else:
            self.common_options += [opt, value]