def not_supported_feature(feature, action=None):
    """
    Returns a templated note for the specified feature indicating that it is not supported.

    Parameters
    ----------

    feature : string
        Specifies the feature that is not supported. This will be inserted into the templated note message.

    action : string, optional
        Specifies if an action is taken for the not supported feature.

    Returns
    -------
    warning_message : str

    """
    if action is None:
        return '*** NOTE: ' + feature + ' is not supported yet.'
    else:
        return ('*** NOTE: ' + feature +
            ' is not supported yet. We took the following action: ' + action)
