def setcadir():
    global ca_dir
    if not ca_dir:
        ca_dir = prompt('Certificate Authority directory: ', default='~/ION_CA')
    if '~' is not ca_dir:
        homedir = os.getenv("HOME")
        ca_dir = os.path.join(homedir, ca_dir.strip('~/'))
dataset/ETHPy150Open ooici/pyon/scripts/fabfile.py/setcadir/operator `in` -> `is not`