code: func (cps ComparablePrincipalSet) Contains(s *ComparablePrincipal) bool {
  	for _, cp := range cps {
  		if cp.IsA(s) {
  			return true
  		}
  	}
  	return false
  }
docs: // Contains returns whether this ComparablePrincipalSet contains the given ComparablePrincipal.
  // A ComparablePrincipalSet X contains a ComparablePrincipal y if
  // there is a ComparablePrincipal x in X such that x.IsA(y).
  // From here it follows that every signature set that satisfies X, also satisfies y.