We must also be able to remove common walls between two cells. Write the function removewalls that accepts two cells and removes the wall that is common between the two (hint: any cell will have at most, one wall in common with another).
e.g. >>> cell1=makecell((0,1))
('cell', (0, 0), ['t', 'r', 'l'])
('cell', (0, 1), ['b', 'r', 'l'])