public function getDataModelDependency()
    {
        if (! $this->exists) {
            return null;
        }

        $dependency = new FieldDataDependency();

        foreach ($this->_fields as $key => $field) {
            if ($field instanceof FieldInterface) {
                $dependsOn = $field->getDataModelDependsOn();

                if ($field->hasDataModelDependencies()) {
                    $dependency->addField($field);
                }
            }
        }

        if ($dependency->getFieldCount()) {
            return $dependency;
        } else {
            return null;
        }
    }