def wfc3_biasfile_filter(kmap):
    """Filter to customize WFC3 BIASFILE for hst_gentools/gen_rmap.py.
    
    Adds precondition_header() hook to rmap header.   Driven by CDBS special case code.
    """
    header_additions = {
        "hooks" : {
            "precondition_header" : "precondition_header_wfc3_biasfile_v1",
            },
        }
    return kmap, header_additions