<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _with(self, option=None):
 """Check if a build option is enabled. If called without argument, it returns all WITH_* items. Example: """

        if option is None:
            return (
                (k, v) for k, v in self.env.items()
                if k.startswith('WITH_')
            )
        return self.env.get('WITH_' + option.upper()) == True