input: Write a function to insert a given string at the beginning of all list items.
  assert insert_prefix(["one", "two", "three"], "prefix_") == ["prefix_one", "prefix_two", "prefix_three"]
  assert insert_prefix(["apple", "banana", "cherry"], "fruit_") == ["fruit_apple", "fruit_banana", "fruit_cherry"]
  assert insert_prefix(["car", "bike"], "vehicle_") == ["vehicle_car", "vehicle_bike"]
output: def insert_prefix(lst, prefix):
      return [prefix + item for item in lst]