input: Write a python function to calculate the total distance of a path consisting of several cities.
  assert path_distance([[0, 0], [1, 1], [2, 3], [3, 2]]) == 4.650281539872885
  assert path_distance([[0, 0], [3, 4], [6, 8]]) == 10.0
  assert path_distance([[1, 1], [4, 5], [9, 6]]) == 10.63014581273465
output: import math
  
  def path_distance(path):
      total_distance = 0
      for i in range(1, len(path)):
          total_distance += math.sqrt((path[i][0] - path[i-1][0])**2 + (path[i][1] - path[i-1][1])**2)
      return total_distance