<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def do_quality(self, quality):
 """Null implementation of quality."""

        if (self.api_version >= '2.0'):
            if (quality != "default"):
                raise IIIFError(code=501, parameter="default",
                                text="Null manipulator supports only quality=default.")
        else:  # versions 1.0 and 1.1
            if (quality != "native"):
                raise IIIFError(code=501, parameter="native",
                                text="Null manipulator supports only quality=native.")