I'm currently using the following script as a validator
import com.atlassian.jira.component.ComponentAccessor
def groupManager = ComponentAccessor.getGroupManager()
groupManager.isUserInGroup(issue.reporter?.name, 'Group1') || groupManager.isUserInGroup(issue.reporter?.name, 'Group2') || groupManager.isUserInGroup(issue.reporter?.name,'Group3')
And I'm getting that warning message. What should I change? Can't find the documentation for it.