code: def make_dummy_streamline(nb_points):
      """Make the streamlines that have been used to create test data files."""
      if nb_points == 1:
          streamline = np.arange(1 * 3, dtype="f4").reshape((1, 3))
          data_per_point = {
              "fa": np.array([[0.2]], dtype="f4"),
              "colors": np.array([(1, 0, 0)] * 1, dtype="f4"),
          }
          data_for_streamline = {
              "mean_curvature": np.array([1.11], dtype="f4"),
              "mean_torsion": np.array([1.22], dtype="f4"),
              "mean_colors": np.array([1, 0, 0], dtype="f4"),
          }
  
      elif nb_points == 2:
          streamline = np.arange(2 * 3, dtype="f4").reshape((2, 3))
          data_per_point = {
              "fa": np.array([[0.3], [0.4]], dtype="f4"),
              "colors": np.array([(0, 1, 0)] * 2, dtype="f4"),
          }
          data_for_streamline = {
              "mean_curvature": np.array([2.11], dtype="f4"),
              "mean_torsion": np.array([2.22], dtype="f4"),
              "mean_colors": np.array([0, 1, 0], dtype="f4"),
          }
  
      elif nb_points == 5:
          streamline = np.arange(5 * 3, dtype="f4").reshape((5, 3))
          data_per_point = {
              "fa": np.array(
                  [[0.5], [0.6], [0.6], [0.7], [0.8]], dtype="f4"
              ),
              "colors": np.array([(0, 0, 1)] * 5, dtype="f4"),
          }
          data_for_streamline = {
              "mean_curvature": np.array([3.11], dtype="f4"),
              "mean_torsion": np.array([3.22], dtype="f4"),
              "mean_colors": np.array([0, 0, 1], dtype="f4"),
          }
  
      return streamline, data_per_point, data_for_streamline
  
imports: import copy
  import operator
  import sys
  import unittest
  import warnings
  from collections import defaultdict
  import numpy
  import pytest
  from numpy.testing import assert_array_almost_equal, assert_array_equal
  from ...testing import assert_arrays_equal, clear_and_catch_warnings
  from ..None import tractogram
  from ..tractogram import LazyDict, LazyTractogram, PerArrayDict, PerArraySequenceDict, Tractogram, TractogramItem, is_data_dict, is_lazy_dict
label_desc: Use image node_id 3 for calling a global function with example usage: make_dummy_streamline(nb_points) and returns: streamline,  data_per_point,  data_for_streamline