input: Write a python function to check if there are any two numbers in a list that sum up to a given number.
  assert sum_check([1, 5, 6, 10, 8, 20], 11) == True
  assert sum_check([1, 2, 3, 4, 5], 10) == False
  assert sum_check([1, 2, 3, 4, 6], 7) == True
output: def sum_check(lst, target):
      seen = set()
      for num in lst:
          if target - num in seen:
              return True
          seen.add(num)
      return False