code: private function getPrefix($parameter)
      {
          $prefix = null;
  
          foreach (array_keys($this->parameterCluster->prefixes) as $_prefix) {
              if (substr($parameter, 0, strlen($_prefix)) == $_prefix) {
                  $prefix = $_prefix;
              }
          }
  
          return $prefix;
      }
docs: Attempts to find the prefix associated with the parameter.
  If no prefix is found, null will be returned.
  
  @param string $parameter
  
  @return string