input: Write a python function to count the number of zeros in a list.
  assert count_zeros([1, 0, 2, 0, 3, 0, 4]) == 3
  assert count_zeros([0, 0, 0, 0, 0]) == 5
  assert count_zeros([1, 2, 3, 4, 5]) == 0
output: def count_zeros(lst):
      return lst.count(0)