def load(obj, env=None, silent=True, key=None, filename=None):
    """
    Reads and loads in to "obj" a single key or all keys from source file.

    :param obj: the settings instance
    :param env: settings current env default='development'
    :param silent: if errors should raise
    :param key: if defined load a single key, else load all in env
    :param filename: Optional custom filename to load
    :return: None
    """
    if toml is None:  # pragma: no cover
        BaseLoader.warn_not_installed(obj, "toml")
        return

    loader = BaseLoader(
        obj=obj,
        env=env,
        identifier="toml",
        extensions=TOML_EXTENSIONS,
        file_reader=toml.load,
        string_reader=toml.loads,
    )
    loader.load(filename=filename, key=key, silent=silent)