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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 add_server(self, name, prefer=False):
 """Add or update an NTP server entry to the node config Args: name (string):
 The IP address or FQDN of the NTP server. prefer (bool):
 Sets the NTP server entry as preferred if True. Returns: True if the operation succeeds, otherwise False. """

        if not name or re.match(r'^[\s]+$', name):
            raise ValueError('ntp server name must be specified')
        if prefer:
            name = '%s prefer' % name
        cmd = self.command_builder('ntp server', value=name)
        return self.configure(cmd)