code: def get_security_group_id(self, name):
          
          # Memoize entire list of groups
          if not hasattr(self, '_security_groups'):
              self._security_groups = {}
              for group in self.get_all_security_groups():
                  self._security_groups[group.name] = group.id
          return self._security_groups[name]
docs: Take name string, give back security group ID.
  
          To get around VPC's API being stupid.