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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _container_init(self):
 """Check if sos is running in a container and perform container specific initialisation based on ENV_HOST_SYSROOT. """

        if ENV_CONTAINER in os.environ:
            if os.environ[ENV_CONTAINER] in ['docker', 'oci']:
                self._in_container = True
        if ENV_HOST_SYSROOT in os.environ:
            self._host_sysroot = os.environ[ENV_HOST_SYSROOT]
        use_sysroot = self._in_container and self._host_sysroot != '/'
        if use_sysroot:
            host_tmp_dir = os.path.abspath(self._host_sysroot + self._tmp_dir)
            self._tmp_dir = host_tmp_dir
        return self._host_sysroot if use_sysroot else None