input: Write a python function to filter names that contain the letter 'a'.
  assert filter_names_with_a(["John", "Paul", "George", "Ringo", "Adam", "Peter", "Alice", "Karen", "Jerry"]) == ["Paul", "Adam", "Alice", "Karen"]
  assert filter_names_with_a(["Ann", "Bob", "Carla", "David"]) == ["Ann", "Carla", "David"]
  assert filter_names_with_a(["Brian", "Megan", "Samantha"]) == ["Megan", "Samantha"]
output: def filter_names_with_a(names):
      return [name for name in names if 'a' in name.lower()]