has method
Implementation
bool has(String a, String b, bool areMutuallyExclusive) {
final key1 = a.compareTo(b) < 0 ? a : b;
final key2 = a.compareTo(b) < 0 ? b : a;
final result = this._data[key1]?[key2];
if (result == null) {
return false;
}
// areMutuallyExclusive being false is a superset of being true, hence if
// we want to know if this PairSet "has" these two with no exclusivity,
// we have to ensure it was added as such.
return areMutuallyExclusive || areMutuallyExclusive == result;
}