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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_attrib_builder(name, container, mapper):
 """Builder for container attributes."""

    context = {'@container': '@{0}'.format(name)}

    def _attrib(type, **kwargs):
        """Define a container attribute."""
        kwargs.setdefault('metadata', {})
        kwargs['metadata'][KEY_CLS] = type
        kwargs['default'] = Factory(container)

        def _converter(value):
            """Convert value to the given type."""
            if isinstance(value, container):
                return mapper(type, value)
            elif value is None:
                return value
            raise ValueError(value)

        kwargs.setdefault('converter', _converter)
        context_ib = context.copy()
        context_ib.update(kwargs.pop('context', {}))
        return attrib(context=context_ib, **kwargs)

    return _attrib