Get element from ArTree by path.

def get_cached_element_by_path(data_tree, path):
    # type: (ArTree, str) -> typing.Optional[_Element]
    """Get element from ArTree by path."""
    if not isinstance(data_tree, ArTree):
        logger.warning("%s not called with ArTree, return None", get_cached_element_by_path.__name__)
        return None
    ptr = data_tree
    for name in path.split('/'):
        if ptr is None:
            return None
        if name.strip():
            ptr = ptr.get_child_by_name(name)
    return ptr.ref if ptr else None