input: Write a function to create a Python generator that returns numbers from a given list. The function should take a list of integers as input and yield each number in the list sequentially.
  assert list_generator([1,3,5,7,9]).send(None)==1
  assert list_generator([2,4,6,8]).send(None)==2
  assert list_generator([0]).send(None)==0
  assert list_generator([]).send(None) is None
output: def list_generator(lst):
      for num in lst:
          yield num