Hi in my code there is a dictionary of dictionary.
nrec={\'bridge\': \'xapi1\', \'current_operations\': {}, \'uuid\': \'9ae5ca7d-e7d6-7a81-f619-d0ea33efb534\', \
Just check
'other_config' in nrec and 'is_guest_installer_network' in nrec['other_config'] and nrec['other_config']['is_guest_installer_network'] == 'true'