##### SUMMARY
group contains call to Display.deprecated or AnsibleModule.deprecate and is scheduled for removal

```
b/ansible/inventory/group.py:54:20: ansible-deprecated-version: Deprecated version ('2.10') found in call to Display.deprecated or AnsibleModule.deprecate
```

##### ISSUE TYPE
 - Bug Report

##### COMPONENT NAME
```
b/ansible/inventory/group.py
```

##### ANSIBLE VERSION
```
2.10
```

##### CONFIGURATION
N/A

##### OS / ENVIRONMENT
N/A

##### STEPS TO REPRODUCE
N/A

##### EXPECTED RESULTS
N/A

##### ACTUAL RESULTS
N/A

if self._hosts is None:
            self._hosts = set(self.hosts)
        return self._hosts
    def get_name(self):
        return self.name
    def add_child_group(self, group):
        if self == group:
            raise Exception("can't add group to itself")
        
        if group not in self.child_groups:
            
            start_ancestors = group.get_ancestors()
            new_ancestors = self.get_ancestors()
            if group in new_ancestors:
                raise AnsibleError("Adding group '%s' as child to '%s' creates a recursive dependency loop." % (to_native(group.name), to_native(self.name)))
            new_ancestors.add(self)
            new_ancestors.difference_update(start_ancestors)
            self.child_groups.append(group)
            
            group.depth = max([self.depth + 1, group.depth])
            
            group._check_children_depth()
            
            
            if self.name not in [g.name for g in group.parent_groups]:
                group.parent_groups.append(self)
                for h in group.get_hosts():
                    h.populate_ancestors(additions=new_ancestors)
            self.clear_hosts_cache()
    def _check_children_depth(self):