code: def _find_usage_route_tables(self):
          
          # Route tables per VPC
          tables = defaultdict(int)
          for table in self.conn.describe_route_tables()['RouteTables']:
              tables[table['VpcId']] += 1
              # Entries per route table
              routes = [
                  r for r in table['Routes']
                  if r['Origin'] != 'EnableVgwRoutePropagation'
              ]
              self.limits['Entries per route table']._add_current_usage(
                  len(routes),
                  aws_type='AWS::EC2::RouteTable',
                  resource_id=table['RouteTableId']
              )
          for vpc_id in tables:
              self.limits['Route tables per VPC']._add_current_usage(
                  tables[vpc_id],
                  aws_type='AWS::EC2::VPC',
                  resource_id=vpc_id,
              )
docs: find usage for route tables