code: def mdf(s1, s2):
      """Computes the MDF (Minimum average Direct-Flip) distance
      [Garyfallidis12]_ between two streamlines.
  
      Streamlines must have the same number of points.
  
      Parameters
      ----------
      s1 : 2D array
          A streamline (sequence of N-dimensional points).
      s2 : 2D array
          A streamline (sequence of N-dimensional points).
  
      Returns
      -------
      double
          Distance between two streamlines.
  
      References
      ----------
      .. [Garyfallidis12] Garyfallidis E. et al., QuickBundles a method for
                          tractography simplification, Frontiers in Neuroscience,
                          vol 6, no 175, 2012.
      """
      return dist(MinimumAverageDirectFlipMetric(), s1, s2)
  
imports: import numpy
  from dipy.segment.metricspeed import SumPointwiseEuclideanMetric, MinimumAverageDirectFlipMetric, AveragePointwiseEuclideanMetric, CosineMetric, Metric, dist
label_desc: Use image node_id 1 for calling a global function with example usage: mdf(s1, s2) and returns: dist