partition method
Implementation
MapOptionPartition<K, V> partition() {
final someParts = <K, V>{};
final noneKeys = <K>[];
for (final entry in entries) {
switch (entry.value) {
case Some(value: final v):
someParts[entry.key] = v;
case None():
noneKeys.add(entry.key);
}
}
return (someParts: someParts, noneKeys: noneKeys);
}