code: public function has($id)
      {
          $exists = isset($this->has[$id]) ? $this->has[$id] : false;
  
          if (isset($this->has[$id]) === false) {
              $filter = Injector::I_BINDINGS | Injector::I_DELEGATES;
  
              $filter = $filter | Injector::I_PREPARES | Injector::I_ALIASES;
  
              $filter = $filter | Injector::I_SHARES;
  
              $definitions = $this->injector->inspect($id, $filter);
  
              $definitions = array_filter($definitions);
  
              $exists = ! empty($definitions) ?: class_exists($id);
          }
  
          return $exists;
      }
docs: Returns true if the container can return an entry for the given identifier.
  
  @param  string $id
  @return boolean