def __dir__(self) -> list[str]:
        """Provide method name lookup and completion. Only provide 'public'
        methods.
        """
        extra_attrs = {
            item
            for source in self._attr_sources
            for item in source
            if isinstance(item, str)
        }
        return sorted(set(dir(type(self))) | extra_attrs)
Provide method name lookup and completion. Only provide 'public'
        methods.
        
xarray/core/common.py