How to retrieve the the assignment group name of an incident from servicenow

Hi  Friends,

I need a small help.

Please assume below scenario.

I have created an incident in ServiceNow and assigned that ticket to a particular Assignment Group.

Now I have created a BOT to display the Incident number, status of that incident and ticket assigned to which “Assignment Group” .

My BOT is able to display the :

Incident number 

State of the incident (Example: If ticket is NEW, then BOT displays 1, if ticket is “In progress”, then BOT displays 2 etc etc..)

BUT, BOT can not display the Assignment Group Name of that incident.

 I am getting different different error 

Example: 
'content' expecting 'String' received 'LinkedHashMap'

If I modify something and run, the I get some other error as:

Content can not be NULL.

Please help me how to get the assignment_group name of that incident assigned to.