def METHOD_NAME(alias):
    """Lookup a formatter by alias.
    Returns None if not found.
    """
    for module_name, name, aliases, _, _ in FORMATTERS.values():
        if alias in aliases:
            if name not in _formatter_cache:
                _load_formatters(module_name)
            return _formatter_cache[name]
    for _, cls in find_plugin_formatters():
        if alias in cls.aliases:
            return cls