Return function object for my function.
        raise ProcessorConfigurationError when function could not be resolved.

def get_function(self):
        """
        Return function object for my function.
        raise ProcessorConfigurationError when function could not be resolved.
        """
        if not hasattr(self, '_function'):
            try:
                modname, funcname = self.function.rsplit('.', 1)
                mod = import_module(modname)
                self._function = getattr(mod, funcname)
            except (ImportError, AttributeError, ValueError), err:
                raise ProcessorConfigurationError(err)

        return self._function