original_string: protected function _code($str) {
  		$self=$this;
  		return preg_replace_callback(
  			'/`` (.+?) ``|(?<!\\\\)`(.+?)(?!\\\\)`/',
  			function($expr) use($self) {
  				return '<code>'.
  					$self->esc(empty($expr[1])?$expr[2]:$expr[1]).'</code>';
  			},
  			$str
  		);
  	}
code: protected function _code($str) {
  		$self=$this;
  		return preg_replace_callback(
  			'/`` (.+?) ``|(?<!\\\\)`(.+?)(?!\\\\)`/',
  			function($expr) use($self) {
  				return '<code>'.
  					$self->esc(empty($expr[1])?$expr[2]:$expr[1]).'</code>';
  			},
  			$str
  		);
  	}
code_tokens: protected function _code ( $ str ) { $ self = $ this ; return preg_replace_callback ( '/`` (.+?) ``|(?<!\\\\)`(.+?)(?!\\\\)`/' , function ( $ expr ) use ( $ self ) { return '<code>' . $ self -> esc ( empty ( $ expr [ 1 ] ) ? $ expr [ 2 ] : $ expr [ 1 ] ) . '</code>' ; } , $ str ) ; }
docstring: Process code span
  @return string
  @param $str string
docstring_tokens: Process code span