input: Write a function to suggest a valid Python syntax to calculate the sum of two variables using lambda. If the input consists of two variables, the function should return the output as a lambda function that takes these two variables as input and returns their sum.
  assert calculate_sum_lambda(3, 4)==lambda a, b : a + b
  
output: def calculate_sum_lambda(x, y):
      return lambda a, b: a + b