commonUnion function
Implementation
Map<String, dynamic> commonUnion(Iterable<Map<String, dynamic>> items) {
if (items.isEmpty) return {};
var out = <String, dynamic>{}..addAll(items.first);
for (var i in items) {
for (var k in out.keys.toList()) {
if (out[k] != i[k]) {
out.remove(k);
}
}
if (out.isEmpty) return out;
}
return out;
}