code: private function addRule($data, $ruleType)
  	{
  		if (\is_string($data))
  		{
  			$data = array($data);
  		}
  		elseif (!\is_array($data))
  		{
  			// Do not translate.
  			throw new InvalidArgumentException('Invalid inflector rule data.');
  		}
  
  		foreach ($data as $rule)
  		{
  			// Ensure a string is pushed.
  			array_push($this->rules[$ruleType], (string) $rule);
  		}
  	}
docs: Adds inflection regex rules to the inflector.
  
  @param   mixed   $data      A string or an array of strings or regex rules to add.
  @param   string  $ruleType  The rule type: singular | plural | countable
  
  @return  void
  
  @since   1.0
  @throws  InvalidArgumentException