code: def distance_matrix(a, b, periodic):
      '''Calculate a distrance matrix between coordinates sets a and b
      '''
      a = a
      b = b[:, np.newaxis]
      return periodic_distance(a, b, periodicf distance_matrix(a, b, periodic):
      '''Calculate a distrance matrix between coordinates sets a and b
      '''
      a = a
      b = b[:, np.newaxis]
      return periodic_distance(a, b, periodic)
docs: Calculate a distrance matrix between coordinates sets a and b