input: Write a python function to delete an element from a list at a given index.
  assert delete_element_at_index([1, 2, 3, 4, 5], 3)==[1, 2, 3, 5]
  assert delete_element_at_index([10, 20, 30, 40, 50], 1)==[10, 30, 40, 50]
  assert delete_element_at_index([7, 8, 9], 0)==[8, 9]
output: def delete_element_at_index(lst, index):
      if 0 <= index < len(lst):
          del lst[index]
      return lst