def merge_feed_dict(*feed_dicts):
    """
    Merge all feed dicts into one.

    Args:
        \**feed_dicts: List of feed dicts.  The later ones will override
            values specified in the previous ones.  If a :obj:`None` is
            specified, it will be simply ignored.

    Returns:
        The merged feed dict.
    """
    ret = {}
    for feed_dict in feed_dicts:
        if feed_dict is not None:
            ret.update(feed_dict)
    return ret