I figured it out. In case someone else finds it helpful.
import com.atlassian.jira.ComponentManager
import com.atlassian.jira.user.util.UserUtil
import com.atlassian.crowd.embedded.api.Group
ComponentManager componentManager = ComponentManager.instance
UserUtil userUtil = componentManager.getUserUtil()
Group g_group = userUtil.getGroupObject("GroupNameInSystem")
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