def marker_in_points(points, marker):
    """
    Checks if the marker is in the list of points.
    
    :params points: a list of dict that contains x, y, z
    :params marker: a dict that contains x, y, z
    :returns: index of the matching marker in list
    """

    for index, point in enumerate(points):
        if (
            point["x"] == marker["x"]
            and point["y"] == marker["y"]
            and point["z"] == marker["z"]
        ):
            return index
    return None