dmap: ids in index and columns 
    idxn,coln of dmap -> 1st and 2nd col

def dmap2lin(df,idxn='index',coln='column',colvalue_name='value'):
    """
    dmap: ids in index and columns 
    idxn,coln of dmap -> 1st and 2nd col
    """
#     df.columns.name=coln
    df.index.name=idxn
    return df.reset_index().melt(id_vars=[df.index.name],
                             var_name=coln,value_name=colvalue_name)