def register_module(self, module, namespace=None):
        """
        Register a module.

        :param module: must be a string or a module object to register.
        :type module: str
        :param namespace: Namespace tag. If it is None module will be used as namespace tag
        :type namespace: str
        """
        namespace = namespace if namespace is not None else module \
            if isinstance(module, str) else module.__name__
        self.register_namespace(namespace, module)
Register a module.

        :param module: must be a string or a module object to register.
        :type module: str
        :param namespace: Namespace tag. If it is None module will be used as namespace tag
        :type namespace: str