code: private function prefixNamespace(string $targetFile)
      {
          $pattern = sprintf(
              '/%1$s\\s+(?!(%2$s)|(Composer(\\\\|;)))/',
              'namespace',
              $this->namespacePrefix
          );
          $replacement = sprintf('%1$s %2$s', 'namespace', $this->namespacePrefix);
  
          $this->replace($pattern, $replacement, $targetFile);
      }
docs: Prefix namespace at the given path.
  
  @param string $targetFile
  
  @return void