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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 _get_add_trustee_cmd(self, trustee):
        '''Get tmsh command to add a trusted device.

        :param trustee: ManagementRoot object -- device to add as trusted
        :returns: str -- tmsh command to add trustee
        '''

        trustee_info = pollster(get_device_info)(trustee)
        username = trustee._meta_data['username']
        password = trustee._meta_data['password']
        return 'tmsh::modify cm trust-domain Root ca-devices add ' \
            '\\{ %s \\} name %s username %s password %s' % \
            (trustee_info.managementIp, trustee_info.name, username, password)