original_string: public function normalizeHeaderKey(string $key)
      {
          $key = strtr(strtolower($key), '_', '-');
          if (strpos($key, 'http-') === 0) {
              $key = substr($key, 5);
          }
          return $key;
      }
code: public function normalizeHeaderKey(string $key)
      {
          $key = strtr(strtolower($key), '_', '-');
          if (strpos($key, 'http-') === 0) {
              $key = substr($key, 5);
          }
          return $key;
      }
code_tokens: public function normalizeHeaderKey ( string $ key ) { $ key = strtr ( strtolower ( $ key ) , '_' , '-' ) ; if ( strpos ( $ key , 'http-' ) === 0 ) { $ key = substr ( $ key , 5 ) ; } return $ key ; }
docstring: Normalize header name
  
  This method transforms header names into a
  normalized form. This is how we enable case-insensitive
  header names in the other methods in this class.
  
  @param  string $key The case-insensitive header name
  
  @return string Normalized header name
docstring_tokens: Normalize header name