func toMap(g *calculation.CoverageList) map[string]calculation.Coverage {
	m := make(map[string]calculation.Coverage)
	for _, cov := range g.Group {
		m[cov.Name] = cov
	}
	return m
}
func toMap(g *calculation.CoverageList) map[string]calculation.Coverage {
	m := make(map[string]calculation.Coverage)
	for _, cov := range g.Group {
		m[cov.Name] = cov
	}
	return m
}
// toMap returns maps the file name to its coverage for faster retrieval
// & membership check