atk4\data\Model::normalizeFieldName PHP Method

    private function normalizeFieldName($field)
    {
        if (is_object($field) && isset($field->_trackableTrait) && $field->owner === $this) {
            $field = $field->short_name;
        }
        if (!is_string($field) || $field === '' || is_numeric($field[0])) {
            throw new Exception(['Incorrect specification of field name', 'arg' => $field]);
        }
        if ($this->only_fields) {
            if (!in_array($field, $this->only_fields)) {
                throw new Exception(['Attempt to use field outside of those set by onlyFields', 'field' => $field, 'only_fields' => $this->only_fields]);
            }
        }
        if ($this->strict_field_check && !isset($this->elements[$field])) {
            throw new Exception(['Field is not defined inside a Model', 'field' => $field, 'model' => $this]);
        }
        return $field;
    }