input: Write a function to identify and fix any bugs in the provided Python code that calculates the sum of elements in a list. If the provided list is empty, return 0.
  assert sum_list([1, 2, 3, 4, 5])==15
  assert sum_list([0, 0, 0, 0])==0
  assert sum_list([-1, -2, -3])==-6
  assert sum_list([])==0
output: def sum_list(lst):
      if not lst:
          return 0
      return sum(lst)