code: def arc_length(angle_1, angle_2, r=1.0):
      """Length of the arc between two angles (in rad) on a circle of
      radius r.
      """
      # Compute the angle between the two inputs between 0 and 2*pi.
      theta = np.mod(angle_2 - angle_1, 2 * pi)
      if theta > pi:
          theta = theta - 2 * pi
      # Return the length of the arc
      L = r * np.abs(theta)
      return L
  
file_path: tslearn/docs/examples/metrics/plot_lcss_custom_metric.py
imports: import numpy
  from numpy import pi
  from sklearn.metrics import pairwise_distances
  import matplotlib.pyplot
  from matplotlib.colors import LinearSegmentedColormap
  from tslearn.generators import random_walks
  from tslearn import metrics
  from tslearn.preprocessing import TimeSeriesScalerMeanVariance
label_desc: Use image node_id 1 for calling a global function with example usage: arc_length(angle_1, angle_2, r) and returns: L