class_docstr: Trajectory compound by time frames and (x, y) pixels.
  
  It's designed as an interpolator, so you can get the position at a given
  time ``t``. You can instantiate it from a file using the methods
  ``from_file`` and ``load_list``.
  
  
  Parameters
  ----------
  
  tt : list or numpy.ndarray
    Time frames.
  
  xx : list or numpy.ndarray
    X positions in the trajectory.
  
  yy : list or numpy.ndarray
    Y positions in the trajectory.
  
  
  Examples
  --------
  
  >>> trajectory = Trajectory([0, .166, .333], [554, 474, 384], [100, 90, 91])
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docstr: Saves a set of trajectories into a text file.
  
  Parameters
  ----------
  
  trajs : list
    List of trajectories to be saved.
  
  filename : str
    Path of the text file that will store the trajectories data.
docstr_tok: ["Saves","a","set","of","trajectories","into","a","text","file",".","Parameters","--","--","--","--","--","trajs",":","list","List","of","trajectories","to","be","saved",".","filename",":","str","Path","of","the","text","file","that","will","store","the","trajectories","data","."]
code: def save_list(trajs, filename):
      """Saves a set of trajectories into a text file.
  
      Parameters
      ----------
  
      trajs : list
        List of trajectories to be saved.
  
      filename : str
        Path of the text file that will store the trajectories data.
      """
      N = len(trajs)
      arr = np.hstack([np.array(list(t.txy(tms=True))) for t in trajs])
      np.savetxt(
          filename,
          arr,
          fmt="%d",
          delimiter="\t",
          header="\t".join(N * ["t(ms)", "x", "y"]),
      )
  
file_path: moviepy/moviepy/video/tools/interpolators.py
imports: import numpy
label_desc: Use image node_id 9 for calling the Trajectory obj's underlying member method code with example usage: obj.save_list(trajs, filename) without return types