input: Write a function to create a lambda function that calculates the sum of two variables and returns the result.
  assert calculate_sum(3, 4) == 7
  assert calculate_sum(0, 0) == 0
  assert calculate_sum(-1, 1) == 0
  assert calculate_sum(10, -5) == 5
  assert calculate_sum(7, 3) == 10
output: calculate_sum = lambda x, y: x + y