input: Write a python function to generate a list of squares of numbers from 0 to n-1 using list comprehension.
  assert generate_squares(5) == [0, 1, 4, 9, 16]
  assert generate_squares(3) == [0, 1, 4]
  assert generate_squares(7) == [0, 1, 4, 9, 16, 25, 36]
output: def generate_squares(n):
      return [i**2 for i in range(n)]