input: Write a python function to determine the quantity of negative numbers within a list.
  assert neg_count([-1,-2,3,-4,-5]) == 4
  assert neg_count([1,2,3]) == 0
  assert neg_count([1,2,-3,-10,20]) == 2
output: def neg_count(lst):
      return sum(1 for x in lst if x < 0)