def METHOD_NAME(arrays, **given):
    """Returns the set of keyword arguments that can be used to filter
    This is just to format a helpful error message for users to show them
    what params they could use to select the right array.
    """
    # return name and epoch if not given by the user
    keys = set(k for k in ("name", "epoch") if given.pop(k, None) is None)
    # add all of the params found in _any_ array
    return (keys | set(
        p.Name for arr in arrays for
        p in arr.parentNode.getElementsByTagName(Param.tagName)
    )) - set(given.keys())