input: Write a function to calculate the sum of a sequence of integers. The function should take a list of integers as input and return the sum of all integers in the list. If the list is empty, the function should return 0.
  
  Example:
  
  assert sum_sequence([1, 2, 3, 4, 5]) == 15
  assert sum_sequence([0, -1, 2, -3, 4]) == 2
  assert sum_sequence([]) == 0
  
output: def sum_sequence(lst):
      return sum(lst)