def _has_attr(node, attr):
    """
    Given a ``node`` and an ``attr``, check if the ``attr`` exists on the
    ``node``.

    :param node: Node
    :type node: :class:`~nuke.Node`
    :param attr: UUID attribute
    :type attr: str
    """
    if attr in node.knobs():
        return True
    return False