def set_obj_coef(me, xid, v):
    """set_obj_coef with transparent index mapping."""
    if xid == 0:
        return me._set_obj_coef(xid, v)
    xid = me._colmap.map(xid) if xid else xid
    if xid > 0:
        return me._set_obj_coef(xid, v)
