atk4\data\Reference::guessFieldType PHP Method

    public function guessFieldType($their_field = null)
    {
        return;
        if (!is_string($their_field)) {
            return;
        }
        // We shouldn't traverse into ourselves recursively
        $cl = get_class($this->owner) . '::' . $this->short_name;
        // see where we shouldn't traverse
        if (isset($this->owner->_do_not_traverse_into)) {
            $dnti = $this->owner->_do_not_traverse_into;
            if (isset($dnti[$cl])) {
                return;
            }
        }
        $dnti[$cl] = true;
        $m = $this->getModel(['_do_not_traverse_into' => $dnti]);
        $f = $m->hasElement($their_field ?: $this->their_field);
        return $f ? $f->type : null;
    }