Returns filtered list of extensions in this registry

        :param support: Return only extensions with this extension support
                        string, or None to return all extensions.
        :return: list of Extension objects

def get_extensions(self, support=None):
        """Returns filtered list of extensions in this registry

        :param support: Return only extensions with this extension support
                        string, or None to return all extensions.
        :return: list of Extension objects
        """
        return [x for x in self.extensions.values() if support
                and support in x.supported or not support]