merge method
Implementation
void merge(PdfDict<T> other) {
for (final key in other.values.keys) {
final value = other[key]!;
final current = values[key];
if (current == null) {
values[key] = value;
} else if (value is PdfArray && current is PdfArray) {
current.values.addAll(value.values);
current.uniq();
} else if (value is PdfDict && current is PdfDict) {
current.merge(value);
} else {
values[key] = value;
}
}
}