Update dict from several sources at once.

        This is simply a convenience method that can be used as an alternative
        to making several calls to the various
        :meth:`~ConfigLoader.update_from_*` methods.

        Updates will be applied in the order that the parameters are listed
        below, with each source taking precedence over those before it.

        :arg obj: Object or name of object, e.g. 'myapp.settings'.
        :arg yaml_env: Name of an environment variable containing the path to
            a YAML config file.
        :arg yaml_file: Path to a YAML config file, or a file-like object.
        :arg json_env: Name of an environment variable containing the path to
            a JSON config file.
        :arg json_file: Path to a JSON config file, or a file-like object.
        :arg env_namespace: Common prefix of the environment variables
            containing the desired config.

def update_from(
            self,
            obj=None,
            yaml_env=None,
            yaml_file=None,
            json_env=None,
            json_file=None,
            env_namespace=None,
            ):
        """
        Update dict from several sources at once.

        This is simply a convenience method that can be used as an alternative
        to making several calls to the various
        :meth:`~ConfigLoader.update_from_*` methods.

        Updates will be applied in the order that the parameters are listed
        below, with each source taking precedence over those before it.

        :arg obj: Object or name of object, e.g. 'myapp.settings'.
        :arg yaml_env: Name of an environment variable containing the path to
            a YAML config file.
        :arg yaml_file: Path to a YAML config file, or a file-like object.
        :arg json_env: Name of an environment variable containing the path to
            a JSON config file.
        :arg json_file: Path to a JSON config file, or a file-like object.
        :arg env_namespace: Common prefix of the environment variables
            containing the desired config.
        """
        if obj:
            self.update_from_object(obj)
        if yaml_env:
            self.update_from_yaml_env(yaml_env)
        if yaml_file:
            self.update_from_yaml_file(yaml_file)
        if json_env:
            self.update_from_json_env(json_env)
        if json_file:
            self.update_from_json_file(json_file)
        if env_namespace:
            self.update_from_env_namespace(env_namespace)