input: Write a function that calculates the sum of two variables using lambda function. The function should take two numbers as input and return the lambda function that sums them up. Provide assert statements to test the function.
  
  assert calculate_sum_lambda(3, 4)(3, 4)==7
  assert calculate_sum_lambda(0, 0)(0, 0)==0
  assert calculate_sum_lambda(-1, 1)(-1, 1)==0
output: def calculate_sum_lambda(a, b):
      return lambda x, y: x + y