original_string: protected function getSortableColumns()
      {
          if ($this->sortableColumns !== null) {
              return $this->sortableColumns;
          }
  
          $columns = $this->getColumns();
          $sortable = array_filter($columns, function ($column) {
              return $column->sortable;
          });
  
          return $this->sortableColumns = $sortable;
      }
code: protected function getSortableColumns()
      {
          if ($this->sortableColumns !== null) {
              return $this->sortableColumns;
          }
  
          $columns = $this->getColumns();
          $sortable = array_filter($columns, function ($column) {
              return $column->sortable;
          });
  
          return $this->sortableColumns = $sortable;
      }
code_tokens: protected function getSortableColumns ( ) { if ( $ this -> sortableColumns !== null ) { return $ this -> sortableColumns ; } $ columns = $ this -> getColumns ( ) ; $ sortable = array_filter ( $ columns , function ( $ column ) { return $ column -> sortable ; } ) ; return $ this -> sortableColumns = $ sortable ; }
docstring: Returns a collection of columns which are sortable.
docstring_tokens: Returns a collection of columns which are sortable .