How to use the gssapi.InitContext function in gssapi

gssapi.C_DELEG_FLAG,
                )
            else:
                gss_flags = (
                    gssapi.C_PROT_READY_FLAG,
                    gssapi.C_INTEG_FLAG,
                    gssapi.C_DELEG_FLAG,
                )
            # Initialize a GSS-API context.
            ctx = gssapi.Context()
            ctx.flags = gss_flags
            krb5_oid = gssapi.OID.mech_from_string(self.krb5_mech)
            target_name = gssapi.Name(
                "host@" + self.targ_name, gssapi.C_NT_HOSTBASED_SERVICE
            )
            gss_ctxt = gssapi.InitContext(
                peer_name=target_name, mech_type=krb5_oid, req_flags=ctx.flags
            )
            if self.server_mode:
                c_token = gss_ctxt.step(c_token)
                gss_ctxt_status = gss_ctxt.established
                self.assertEquals(False, gss_ctxt_status)
                # Accept a GSS-API context.
                gss_srv_ctxt = gssapi.AcceptContext()
                s_token = gss_srv_ctxt.step(c_token)
                gss_ctxt_status = gss_srv_ctxt.established
                self.assertNotEquals(None, s_token)
                self.assertEquals(True, gss_ctxt_status)
                # Establish the client context
                c_token = gss_ctxt.step(s_token)
                self.assertEquals(None, c_token)
            else:

"host@" + self._gss_host, gssapi.C_NT_HOSTBASED_SERVICE
        )
        ctx = gssapi.Context()
        ctx.flags = self._gss_flags
        if desired_mech is None:
            krb5_mech = gssapi.OID.mech_from_string(self._krb5_mech)
        else:
            mech, __ = decoder.decode(desired_mech)
            if mech.__str__() != self._krb5_mech:
                raise SSHException("Unsupported mechanism OID.")
            else:
                krb5_mech = gssapi.OID.mech_from_string(self._krb5_mech)
        token = None
        try:
            if recv_token is None:
                self._gss_ctxt = gssapi.InitContext(
                    peer_name=targ_name,
                    mech_type=krb5_mech,
                    req_flags=ctx.flags,
                )
                token = self._gss_ctxt.step(token)
            else:
                token = self._gss_ctxt.step(recv_token)
        except gssapi.GSSException:
            message = "{} Target: {}".format(sys.exc_info()[1], self._gss_host)
            raise gssapi.GSSException(message)
        self._gss_ctxt_status = self._gss_ctxt.established
        return token

principal
       The service principal
    host
       Host url where we would like to authenticate
    domain
       Kerberos user domain
    '''

    if not HAS_GSSAPI:
        raise ImportError('The gssapi library is not imported.')

    service = '{0}/{1}@{2}'.format(principal, host, domain)
    log.debug('Retrieving gsspi token for service {0}'.format(service))
    service_name = gssapi.Name(service, gssapi.C_NT_USER_NAME)
    ctx = gssapi.InitContext(service_name)
    in_token = None
    while not ctx.established:
        out_token = ctx.step(in_token)
        if out_token:
            if six.PY2:
                return base64.b64encode(out_token)
            return base64.b64encode(salt.utils.stringutils.to_bytes(out_token))
        if ctx.established:
            break
        if not in_token:
            raise salt.exceptions.CommandExecutionError(
                'Can\'t receive token, no response from server')
    raise salt.exceptions.CommandExecutionError(
        'Context established, but didn\'t receive token')

targ_name = gssapi.Name("host@" + self._gss_host,
                                gssapi.C_NT_HOSTBASED_SERVICE)
        ctx = gssapi.Context()
        ctx.flags = self._gss_flags
        if desired_mech is None:
            krb5_mech = gssapi.OID.mech_from_string(self._krb5_mech)
        else:
            mech, __ = decoder.decode(desired_mech)
            if mech.__str__() != self._krb5_mech:
                raise SSHException("Unsupported mechanism OID.")
            else:
                krb5_mech = gssapi.OID.mech_from_string(self._krb5_mech)
        token = None
        try:
            if recv_token is None:
                self._gss_ctxt = gssapi.InitContext(peer_name=targ_name,
                                                    mech_type=krb5_mech,
                                                    req_flags=ctx.flags)
                token = self._gss_ctxt.step(token)
            else:
                token = self._gss_ctxt.step(recv_token)
        except gssapi.GSSException:
            raise gssapi.GSSException("{0} Target: {1}".format(sys.exc_info()[1],
                                                               self._gss_host))
        self._gss_ctxt_status = self._gss_ctxt.established
        return token