system/Config/Services.php
public static function validation(\Config\Validation $config = null, bool $getShared = true)
	{
		if ($getShared)
		{
			return static::getSharedInstance('validation', $config);
		}

		if (is_null($config))
		{
			$config = config('Validation');
		}

		return new Validation($config, static::renderer());
	}
public static function validation(\Config\Validation $config = null, bool $getShared = true)
	{
		if ($getShared)
		{
			return static::getSharedInstance('validation', $config);
		}

		if (is_null($config))
		{
			$config = config('Validation');
		}

		return new Validation($config, static::renderer());
	}
The Validation class provides tools for validating input data.

@param \Config\Validation $config
@param boolean            $getShared

@return \CodeIgniter\Validation\Validation