system/Language/Language.php
public function setLocale(string $locale = null)
	{
		if (! is_null($locale))
		{
			$this->locale = $locale;
		}

		return $this;
	}
public function setLocale(string $locale = null)
	{
		if (! is_null($locale))
		{
			$this->locale = $locale;
		}

		return $this;
	}
Sets the current locale to use when performing string lookups.

@param string $locale

@return $this