It's quite easy to define a new abstract class using the ABC metaclass. The following code snippet shows an example of achieving this kind of behavior:

import abc

class Handler(metaclass=abc.ABCMeta):
    """Handler provides an interface to build handlers."""

    def __init__(self, handler=None):
        """Initialize the handler.

        Keyword arguments:
        handler -- The next handler object to be called
        """

        self._next_handler = handler

    @abc.abstractmethod
    def handler(self, data):
        """The handler abstract method.

        Keyword arguments:
        data -- The data to be processed by the handler
        """

        pass