input: Write a function to identify and fix any bugs in the provided Python code for calculating the sum of a list. The original code is shown below:
  
  ### Input:
  def sum_list(list):
      sum_list = 0
      for num in list:
          sum_list += num
      return sum
  
  ### Fixed Output:
  def sum_list(list):
      sum_list = 0
      for num in list:
          sum_list += num
      return sum_list
  
  assert sum_list([1, 2, 3, 4, 5])==15
  assert sum_list([-1, -2, -3, -4])==-10
  assert sum_list([])==0
  assert sum_list([10, -10, 10, -10])==0
  assert sum_list([1, 2, 3, -3, -2, -1])==0
output: def sum_list(list):
      sum_list = 0
      for num in list:
          sum_list += num
      return sum_list