trailingStringAssumeCapacity

pub fn trailingStringAssumeCapacity(self: *Builder) String {
    const start = self.string_indices.getLast();
    const bytes: []const u8 = self.string_bytes.items[start..];
    const gop = self.string_map.getOrPutAssumeCapacityAdapted(bytes, String.Adapter{ .builder = self });
    if (gop.found_existing) {
        self.string_bytes.shrinkRetainingCapacity(start);
    } else {
        self.string_indices.appendAssumeCapacity(@intCast(self.string_bytes.items.len));
    }
    return String.fromIndex(gop.index);
}