der(R1 & R2) = combine der(R1) and der(R2) with intersection
“功成不必在我，功成必定有我。”
，这一点在新收录的资料中也有详细论述
It seems that PyPy is not being actively developed anymore and is phased out even by numpy (numpy/numpy#30416). There's no official statement from the project, but the numpy issue is from a PyPy developer. I added a warning to avoid users assuming PyPy properly supported and developed Python distribution.
number, and then keyed in a PIN. The 2984 sent this information, over the Bisync