Getting "undefined" while trying to fetch value on field on transition screen for jira workflow validator using Forge


I am trying to use forge workflow validator module to validate a condition based on the value of “resolution” which is on the transition screen. According to the documentation i can use “issue” context variable to get the value. When i try to access it, it shows undefined. But i can get values which arent on transition screen using the same. Any idea on how to get values of fields on transition screen? This is the code i am using:

export const run = args => {
  const res = args.issue.resolution;
  return {
    result: args.issue.assignee!=null,
    errorMessage: 'Only PRO project can use this flow'