Problems with script errata and library usage

[alanZee]

Thanks for providing such a pyJHTDB library to make it easy to get relevant data, but I found some problems in using it:

    1. In the script pyJHTDB-master/pyJHTDB/test.py, line 127, the getFunction parameter is filled in incorrectly, according to the context, it should be the parameter to get the pressure gradient, but it is written to get the velocity gradient

    2. The getData() method often returns an incorrect array when getting a slightly larger slice of the pressure gradient (even if it gets the same batch of points and the code is the same each time)