about the format of input formula

[andeyeluguo]

Hi，it is really a great job.
Now I am reading this code, and have this questions:
what's the format of the input formula?
As I know, it is not the real latex format, because it has no '$$' to warp the formula.
like this examples

mathQ/data/18.03/18.03_Question_06.json

Line 4 in 8faf02f

"Original question": "The problem pertains to the solution of differential equations with complex coefficients. Find a general solution of y'' \u2212 2iy' + 3y = 0.",

I do not know what's the meaning of \u code