'Invoke this Action on the specified AppCfg.
This calls the function of the appropriate name on AppCfg, and
respects polymophic overrides.
Args:
appcfg: The appcfg to use.
Returns:
The result of the function call.'

def __call__(self, appcfg):

    method = getattr(appcfg, self.function)
    return method()
