system/Config/Services.php
public static function migrations(BaseConfig $config = null, ConnectionInterface $db = null, bool $getShared = true)
	{
		if ($getShared)
		{
			return static::getSharedInstance('migrations', $config, $db);
		}

		$config = empty($config) ? new Migrations() : $config;

		return new MigrationRunner($config, $db);
	}
public static function migrations(BaseConfig $config = null, ConnectionInterface $db = null, bool $getShared = true)
	{
		if ($getShared)
		{
			return static::getSharedInstance('migrations', $config, $db);
		}

		$config = empty($config) ? new Migrations() : $config;

		return new MigrationRunner($config, $db);
	}
@param \CodeIgniter\Config\BaseConfig            $config
@param \CodeIgniter\Database\ConnectionInterface $db
@param boolean                                   $getShared

@return \CodeIgniter\Database\MigrationRunner