input: Write a function to calculate the sum of two variables using lambda. The function should take two arguments and return the sum.
  assert calculate_sum(3, 4)==7
  assert calculate_sum(0, 0)==0
  assert calculate_sum(-1, 1)==0
  assert calculate_sum(-2, -3)==-5
  assert calculate_sum(5, -5)==0
output: calculate_sum = lambda x, y: x + y