code: func (cps ComparablePrincipalSet) IsContainedIn(set ComparablePrincipalSet) bool {
  	for _, cp := range cps {
  		if !set.Contains(cp) {
  			return false
  		}
  	}
  	return true
  }
docs: // IsContainedIn returns whether this ComparablePrincipalSet is contained in the given ComparablePrincipalSet.
  // More formally- a ComparablePrincipalSet X is said to be contained in ComparablePrincipalSet Y
  // if for each ComparablePrincipalSet x in X there is a ComparablePrincipalSet y in Y such that y.IsA(x) is true.
  // If a ComparablePrincipalSet X is contained by a ComparablePrincipalSet Y then if a signature set satisfies Y,
  // it also satisfies X, because for each x in X there is a y in Y such that there exists a signature of a corresponding
  // identity such that the identity satisfies y, and therefore satisfies x too.