code: def expand_fc_groups(users):
      
      groups = None
      for user in users:
          fcgroup = None
          if '@' not in user:
              fcgroup = user
          elif user.lower().endswith('@firecloud.org'):
              if groups is None:
                  r = fapi.get_groups()
                  fapi._check_response_code(r, 200)
                  groups = {group['groupEmail'].lower():group['groupName'] \
                            for group in r.json() if group['role'] == 'Admin'}
              if user.lower() not in groups:
                  if fcconfig.verbosity:
                      eprint("You do not have access to the members of {}".format(user))
                  yield user
                  continue
              else:
                  fcgroup = groups[user.lower()]
          else:
              yield user
              continue
          r = fapi.get_group(fcgroup)
          fapi._check_response_code(r, 200)
          fcgroup_data = r.json()
          for admin in fcgroup_data['adminsEmails']:
              yield admin
          for member in fcgroup_data['membersEmails']:
              yield member
docs: If user is a firecloud group, return all members of the group.
      Caveat is that only group admins may do this.