original_string: protected function getNestedFormFieldKeys(ModelFormLayoutNodeInterface $node = null): array
      {
          if (null === $node) {
              $children = $this->layout();
          } else {
              $children = $node->children();
          }
  
          $fieldKeys = [];
  
          foreach ($children as $key => $value) {
  
              if ($value instanceof ModelFormLayoutNodeInterface) {
                  $fieldKeys = array_merge($fieldKeys, $this->getNestedFormFieldKeys($value));
                  continue;
              }
  
              if (is_string($value)) {
                  $fieldKeys[] = $value;
              }
          }
  
          return $fieldKeys;
      }
code: protected function getNestedFormFieldKeys(ModelFormLayoutNodeInterface $node = null): array
      {
          if (null === $node) {
              $children = $this->layout();
          } else {
              $children = $node->children();
          }
  
          $fieldKeys = [];
  
          foreach ($children as $key => $value) {
  
              if ($value instanceof ModelFormLayoutNodeInterface) {
                  $fieldKeys = array_merge($fieldKeys, $this->getNestedFormFieldKeys($value));
                  continue;
              }
  
              if (is_string($value)) {
                  $fieldKeys[] = $value;
              }
          }
  
          return $fieldKeys;
      }
code_tokens: protected function getNestedFormFieldKeys ( ModelFormLayoutNodeInterface $ node = null ) : array { if ( null === $ node ) { $ children = $ this -> layout ( ) ; } else { $ children = $ node -> children ( ) ; } $ fieldKeys = [ ] ; foreach ( $ children as $ key => $ value ) { if ( $ value instanceof ModelFormLayoutNodeInterface ) { $ fieldKeys = array_merge ( $ fieldKeys , $ this -> getNestedFormFieldKeys ( $ value ) ) ; continue ; } if ( is_string ( $ value ) ) { $ fieldKeys [ ] = $ value ; } } return $ fieldKeys ; }
docstring: Returns a list of form field keys recursively for a given layout node.
  
  @param ModelFormLayoutNodeInterface $node
  @return string[]
docstring_tokens: Returns a list of form field keys recursively for a given layout node .