def listcollections(elvisresponse):
    """
    Create a dictionary of 'data collections' in ELVIS.

    Input: a dictionary comprising the "available_data" element of
    an ELVIS response package

    Output: a dictionary like

    {
    0 : "NSW Government",
    1 : "ACT Government",
    ...
    7 : "Geoscience Australia"
    }

    """
    i = 0
    collections = {}
    while i < len(elvisresponse):
        collections.update( {i : elvisresponse[i]["source"] } )
        i+=1
    return collections