input: Write a function to create a Python generator that returns numbers from a given list. The function should iterate through each item in the input list and yield it.
  assert list_generator([1,3,5,7,9])==gen
  assert list_generator([2,4,6,8])==gen
  assert list_generator([])==gen
  assert list_generator([10])==gen
output: def list_generator(lst):
      for item in lst:
          yield item