```
AttributeError: module 'posthog.queries.sessions' has no attribute 'Sessions'
(6 additional frame(s) were not displayed)
...
  File "posthog/api/dashboard.py", line 101, in get_items
    update_dashboard_items_cache(dashboard)
  File "posthog/tasks/update_cache.py", line 73, in update_dashboard_items_cache
    update_cache_item(cache_key, cache_type, payload)
  File "posthog/tasks/update_cache.py", line 64, in update_cache_item
    result = _calculate_by_filter(filter, key, team_id, cache_type)
  File "posthog/tasks/update_cache.py", line 144, in _calculate_by_filter
    insight_class = import_from(insight_class_path[0], insight_class_path[1])
  File "posthog/tasks/update_cache.py", line 132, in import_from
    return getattr(importlib.import_module(module), name)
```
posthog/settings.py
value = os.getenv(key)
    if value is None:
        if optional:
            return None
        if default is not None:
            return default
        else:
            raise ImproperlyConfigured(f'The environment variable "{key}" is required to run PostHog!')
    if type_cast is not None:
        return type_cast(value)
    return value
def get_list(text: str) -> List[str]: