input: Write a function to create a lambda function that calculates the sum of two given variables. The lambda function should be stored in a variable called `sum` and should take two parameters `a` and `b`. The function should then print the result of calling this lambda function with the provided input values.
  assert sum(3, 4) == 7
  assert sum(2, 1) == 3
  assert sum(0, 0) == 0
  assert sum(-1, 1) == 0
  assert sum(-5, 2) == -3
output: sum = lambda a, b: a + b
  print(sum(3, 4))
  print(sum(2, 1))
  print(sum(0, 0))
  print(sum(-1, 1))
  print(sum(-5, 2))