input: Write a function to provide a one-line improved version of the given python code which calculates the sum of elements in a list. The original function iterates through the list and accumulates the sum manually, but your task is to improve this by using a built-in function for better readability and efficiency.
  
  def sum_elements(arr):
      return sum(arr)
  
  assert sum_elements([1, 2, 3, 4])==10
  assert sum_elements([5, 10, 15])==30
  assert sum_elements([0, 0, 0])==0
  assert sum_elements([])==0
  assert sum_elements([-1, -2, -3, -4])==-10
output: def sum_elements(arr):
      return sum(arr)