code: def _group_get_hostnames(self, group_name):
          
          hostnames = []
  
          hosts_section = self._get_section(group_name, 'hosts')
          if hosts_section:
              for entry in hosts_section['entries']:
                  hostnames.extend(self.expand_hostdef(entry['name']))
  
          children_section = self._get_section(group_name, 'children')
          if children_section:
              for entry in children_section['entries']:
                  hostnames.extend(self._group_get_hostnames(entry['name']))
  
          return hostnames
docs: Recursively fetch a list of each unique hostname that belongs in or
          under the group. This includes hosts in children groups.