input: Write a function to optimize the given Python program that prints each number in a list on a new line. If the input list is empty, the function should return an empty string.
  assert optimize_print_numbers([1, 2, 3, 4, 5, 6])=='1\n2\n3\n4\n5\n6'
  assert optimize_print_numbers([])==''
output: def optimize_print_numbers(lst):
      if not lst:
          return ''
      return '\n'.join(map(str, lst))