input: Write a function to improve the given python code for finding the sum of elements of a list. The function should be optimized for readability and simplicity.
  
  def sum_elements(arr):
      return sum(arr) # return sum of elements of arr with one line of code.
  
  assert sum_elements([1, 2, 3, 4, 5])==15
  assert sum_elements([0, -1, 1])==0
  assert sum_elements([])==0
  assert sum_elements([10, 20, 30])==60
  assert sum_elements([-5, -3, -1, 0, 1, 3, 5])==0
output: def sum_elements(arr):
      return sum(arr)