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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 __find_command_ns(self, command):
 """ Returns the name spaces where the given command named is registered. If the command exists in the default name space, the returned list will only contain the default name space. Returns an empty list of the command is unknown :param command: A command name :return: A list of name spaces """

        # Look for the spaces where the command name appears
        namespaces = []
        for namespace, commands in self._commands.items():
            if command in commands:
                namespaces.append(namespace)

        # Sort name spaces
        namespaces.sort()

        # Default name space must always come first
        try:
            namespaces.remove(DEFAULT_NAMESPACE)
            namespaces.insert(0, DEFAULT_NAMESPACE)
        except ValueError:
            # Default name space wasn't present
            pass

        return namespaces