func (pcs Trace) TrimBelow(pc Call) Trace {
	for len(pcs) > 0 && pcs[0] != pc {
		pcs = pcs[1:]
	}
	return pcs
}
func (pcs Trace) TrimBelow(pc Call) Trace {
	for len(pcs) > 0 && pcs[0] != pc {
		pcs = pcs[1:]
	}
	return pcs
}
// TrimBelow returns a slice of the Trace with all entries below pc removed.