code: public function find($id, $columns = array('*'))
      {
  
          $columnsPassed = (func_num_args() > 1);
  
          $columns = $columnsPassed ? $columns : $this->getQueryColumns();
  
          $query = $this->buildQuery($columns);
  
          if ($columnsPassed) {
              return $query->find($id, $columns);
          }
  
          // addJoinOnce adds queryColumns again...
          return $query->find($id, $this->getQueryColumns());
  
      }
docs: Find a model by its primary key.
  
  @param  mixed  $id
  @param  array  $columns
  @return \Illuminate\Database\Eloquent\Model|static|null