def METHOD_NAME(mast_uri):
    """
    Given a MAST dataURI, return the associated relative path.
    Parameters
    ----------
    mast_uri : str
        The MAST uri.
    Returns
    -------
    response : str
        The associated relative path.
    """
    response = _simple_request("https://mast.stsci.edu/api/v0.1/path_lookup/",
                               {"uri": mast_uri})
    result = response.json()
    uri_result = result.get(mast_uri)
    return uri_result["path"]