XPathSequence.from constructor
Creates a sequence from an iterable, flattening any nested sequences.
Implementation
factory from(Iterable<Object?> items) {
final flat = <XPathItem>[];
_flattenInto(items, flat);
if (flat.isEmpty) return empty;
if (flat.length == 1) return _XPathSingleSequence(flat.first);
return _XPathListSequence(flat);
}