class_docstr: A trajectory of interactions with a RL environment.
  
  Trajectories are created when interacting with an RL environment. They can
  be prolonged and sliced and when completed, allow to re-calculate returns.
class_docstr_tok: ["A","trajectory","of","interactions","with","a","RL","environment",".","Trajectories","are","created","when","interacting","with","an","RL","environment",".","They","can","be","prolonged","and","sliced","and","when","completed",",","allow","to","re-calculate","returns","."]
docstr: Returns the number of observations in the trajectory.
docstr_tok: ["Returns","the","number","of","observations","in","the","trajectory","."]
code: def __len__(self):
      """Returns the number of observations in the trajectory."""
      # We always have 1 more of observations than of everything else.
      return len(self._timesteps) + 1
  
imports: import collections
  import os
  import gin
  import gym
  import numpy
  from trax import fastmath
  from trax.rl import advantages
  from trax.supervised import training
label_desc: Use image node_id 2 for calling the Trajectory obj's underlying member method code with example usage: obj.__len__() and returns: unknown