@property
    def os(self):
        if 'os' in self._values:
            return self._values['os']
        return self._defaults['os']
use getheader() method depending or urllib in use
dataset/ETHPy150Open Microsoft/ApplicationInsights-Python/applicationinsights/channel/contracts/Envelope.py/Envelope.os--crossover with--dataset/ETHPy150Open PaloAltoNetworks/SplunkforPaloAltoNetworks/bin/lib/pan-python/lib/pan/xapi.py/PanXapi.__get_header