input: Write a python function to calculate the sum of elements in a list.
  assert sum_of_elements([1, 2, 3, 4]) == 10
  assert sum_of_elements([10, 20, 30]) == 60
  assert sum_of_elements([5, 5, 5, 5, 5]) == 25
output: def sum_of_elements(lst):
      return sum(lst)