don't replace ref in t_to_g and g_to_t (already in g_to_x and x_to_g)
don't replace ref in t_to_g and g_to_t (already in g_to_x and x_to_g)

biocommons/hgvs,biocommons/hgvs,biocommons/hgvs,biocommons/hgvs