code: private function prefixExists($parameter)
      {
          $prefixExists = false;
  
          foreach (array_keys($this->parameterCluster->prefixes) as $prefix) {
              if (substr($parameter, 0, strlen($prefix)) == $prefix) {
                  $prefixExists = true;
                  break;
              }
          }
  
          return $prefixExists;
      }
docs: Check if the prefix is defined in the parameter cluster.
  
  @param string $parameter
  
  @return bool