code: public function setPluralForm($key, $plural)
  	{
  		if (!is_array($plural))
  			$plural = [$plural];
  
  		if (!$this->msgstr_plural)
  			$this->msgstr_plural = [];
  
  		$this->msgstr_plural[$key] = $plural;
  	}
docs: Sets a particular plural message key
  @param int $key The plural form being set
  @param string|array $plural The plural string