class_docstr: Common functionality of trajectory records.
  
  :param id: ID of the trajectory. Can be a string ID or any other data (like environment seeding information).
docstr: Length of the trajectory
docstr_tok: ["Length","of","the","trajectory"]
code: def __len__(self):
      """Length of the trajectory"""
      return len(self.step_records)
  
imports: from typing import List, Optional, Any, TypeVar, Generic, Dict, Union
  import numpy
  from maze.core.env.action_conversion import ActionType, TorchActionType
  from maze.core.rendering.renderer import Renderer
  from maze.core.trajectory_recording.records.state_record import StateRecord
  from maze.core.trajectory_recording.records.structured_spaces_record import StructuredSpacesRecord, StepKeyType
label_desc: Use image node_id 2 for calling the TrajectoryRecord obj's underlying member method code with example usage: obj.__len__() and returns: len