input: Write a function to generate a list of tuples using list comprehension and nested for loops.
  assert generate_tuples() == [(2, 0), (2, 1), (2, 2), (3, 0), (3, 1), (3, 2), (4, 0), (4, 1), (4, 2)]
output: def generate_tuples():
      return [(i, j) for i in range(2, 5) for j in range(3)]