# Tracker

Trackers maintain the state of a dialogue between the assistant and the user in the form of conversation sessions. To learn more about how to configure the session behavior, check out the docs on [Session configuration](https://legacy-docs-v1.rasa.com/1.10.6/core/domains/#session-config).

## Class `rasa.core.trackers.DialogueStateTracker`
Maintains the state of a conversation.

### Methods

- `applied_events()`  
  Returns all actions that should be applied - w/o reverted events.
  
- `as_dialogue()`  
  Return a `Dialogue` object containing all of the turns.
  
- `change_form_to(form_name)`  
  Activate or deactivate a form.
  
- `clear_followup_action()`  
  Clears follow up action when it was executed.
  
- `copy()`  
  Creates a duplicate of this tracker.
  
- `current_slot_values()`  
  Return the currently set values of the slots.
  
- `current_state(event_verbosity=<EventVerbosity.NONE: 1>)`  
  Return the current tracker state as an object.
  
- `events_after_latest_restart()`  
  Return a list of events after the most recent restart.
  
- `export_stories(e2e=False, include_source=False)`  
  Dump the tracker as a story in the Rasa Core story format.
  
- `export_stories_to_file(export_path='debug.md')`  
  Dump the tracker as a story to a file.
  
- `from_dict(sender_id, events_as_dict, slots=None, max_event_history=None)`  
  Create a tracker from dump.
  
- `generate_all_prior_trackers()`  
  Returns a generator of the previous trackers of this tracker.
  
- `get_last_event_for(event_type, action_names_to_exclude=None, skip=0)`  
  Gets the last event of a given type which was actually applied.
  
- `get_latest_entity_values(entity_type, entity_role=None, entity_group=None)`  
  Get entity values found for the passed entity type and optional role and group in latest message.
  
- `get_latest_input_channel()`  
  Get the name of the input_channel of the latest UserUttered event.
  
- `get_slot(key)`  
  Retrieves the value of a slot.
  
- `idx_after_latest_restart()`  
  Return the idx of the most recent restart in the list of events.
  
- `init_copy()`  
  Creates a new state tracker with the same initial values.
  
- `is_paused()`  
  State whether the tracker is currently paused.
  
- `last_executed_action_has(name, skip=0)`  
  Returns whether last ActionExecuted event had a specific name.
  
- `past_states(domain)`  
  Generate the past states of this tracker based on the history.
  
- `recreate_from_dialogue(dialogue)`  
  Use a serialised Dialogue to update the trackers state.
  
- `reject_action(action_name)`  
  Notify active form that it was rejected.
  
- `replay_events()`  
  Update the tracker based on a list of events.
  
- `set_form_validation(validate)`  
  Toggle form validation.
  
- `set_latest_action_name(action_name)`  
  Set latest action name and reset form validation and rejection parameters.
  
- `travel_back_in_time(target_time)`  
  Creates a new tracker with a state at a specific timestamp.
  
- `trigger_followup_action(action)`  
  Triggers another action following the execution of the current.
  
- `update(event, domain=None)`  
  Modify the state of the tracker according to an `Event`.

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