interface.py

import abc


class Plugin(object):
    
    __metaclass__ = abc.ABCMeta
    
    @abc.abstractmethod
    def this_method_is_required(self, foo):
        pass
    
    
class SpecificVideoPlugin(Plugin):
    
    def this_method_is_required(self, foo):
        return foo[::-1]
    
    
# Trying to instantiate the interface directly will result in an exception
plugin = Plugin()

# However instantiating the subclass will work because it overrode the abstract method
plugin = SpecificVideoPlugin()