input: 
  def calculate_sum(a: int, b: int) -> int:
      """Calculates the sum of two integers a and b using a lambda function.
      >>> calculate_sum(3, 4)
      7
      >>> calculate_sum(0, -1)
      -1
      """
      sum = lambda x, y: x + y
      return sum(a, b)
  
output:     sum = lambda x, y: x + y
      return sum(a, b)