def METHOD_NAME(container):
    # type: (AnySettingsContainer) -> str
    """
    Obtains the defined operation configuration mode.
    :returns: one value amongst :py:data:`weaver.config.WEAVER_CONFIGURATIONS`.
    """
    settings = get_settings(container)
    weaver_config = settings.get("weaver.configuration")
    if not weaver_config:
        LOGGER.warning("Setting 'weaver.configuration' not specified, using '%s'", WeaverConfiguration.DEFAULT)
        weaver_config = WeaverConfiguration.DEFAULT
    weaver_config_up = weaver_config.upper()
    if weaver_config_up not in WeaverConfiguration:
        raise ConfigurationError(f"Unknown setting 'weaver.configuration' specified: '{weaver_config}'")
    return weaver_config_up