human
Complete this python program:
def make_contrib(superclass, func=None):
assistant
#Here is the Python program you requested.

    """Returns a suitable contribute_to_class() method for the Field subclass.
    If \func\ is passed in, it is the existing contribute_to_class() method on
    the subclass and it is called before anything else. It is assumed in this
    case that the existing contribute_to_class() calls all the necessary
    superclass methods.
    """
    def contribute_to_class(self, cls, name):
        if func:
            func(self, cls, name)
        else:
            super(superclass, self).contribute_to_class(cls, name)
        setattr(cls, self.name, Creator(self))
    return contribute_to_class