/**
  * Add a basic where clause to the query.
  *
  * @param  string  $column
  * @param  string  $operator
  * @param  mixed   $value
  * @param  string  $boolean
  * @return $this
  */
 public function where($column, $operator = null, $value = null, $boolean = 'and')
 {
     if ($column instanceof Closure) {
         $query = $this->model->newQueryWithoutScopes();
         call_user_func($column, $query);
         $this->query->addNestedWhereQuery($query->getQuery(), $boolean);
     } else {
         call_user_func_array(array($this->query, 'where'), func_get_args());
     }
     return $this;
 }