'Ensure that builtins are not modified.'

def sentry_modified_builtin(self, inst, gvar):

    if ((gvar.name in ('range', 'xrange')) and (gvar.value not in utils.RANGE_ITER_OBJECTS)):
        bad = True
    elif ((gvar.name == 'slice') and (gvar.value is not slice)):
        bad = True
    elif ((gvar.name == 'len') and (gvar.value is not len)):
        bad = True
    else:
        bad = False
    if bad:
        raise TypingError(("Modified    builtin    '%s'" % gvar.name), loc=inst.loc)
