new_contents: from greengraph import Greengraph
  import numpy as np
  
  mygraph=Greengraph('New York','Chicago')
  start = [0,0]
  end = [1,1]
  array1 = np.array([start])
  array2 = np.array([start, end])
  assert not mygraph.location_sequence(start,end,0)
  assert np.all(mygraph.location_sequence(start,end,1)==array1)
  assert np.all(mygraph.location_sequence(start,end,2)==array2)
  
subject: Include a unit test for the location_sequence method in Greengraph.