def _mask_crc(crc):
  return (((crc >> 15) | (crc << 17)) + _CRC_MASK_DELTA) & 0xFFFFFFFFL
Ensures valid `docstatus` transition.
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/api/files/records.py/_mask_crc--crossover with--dataset/ETHPy150Open frappe/frappe/frappe/model/document.py/Document.check_docstatus_transition