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Description
An annotated statement is a statement that carries subject and snak plus a set of annotation records.
If we introduce AnnotatedStatement's we could update Store.filter() to return an iterator of such statements (instead of an iterator of pairs). Note that Store.get_annotations() could be kept as is.
One further advantage of AnnotatedStatement is that it eases the serialization of statement objects to RDF (not currently implemented). Without annotated statements, stmt.to_rdf() would need to received extra arguments for the associated annotations.