Now uses adafruit_pixelbuf
_pixelbuf was renamed to adafruit_pixelbuf in CircuitPython 7.0. adafruit_pypixelbuf has been migrated to adafruit_pixelbuf. This library will maintain backwards compatibility with _pixelbuf and adafruit_pypixelbuf until such time as it is no longer necessary.
To use in CircuitPython, simply install the Adafruit CircuitPython bundle.
To use in CPython, pip3 install adafruit-circuitpython-neopixel.
Read the docs for info on how to use it.