An abstract, {@link it.unimi.dsi.io.SafelyCloseable safely closeable} implementation of a document.
This implementation provides also a {@link #toString()} method that just returns the document {@linkplain it.unimi.dsi.mg4j.document.Document#title() title}.
Note that even if your {@link it.unimi.dsi.mg4j.document.Document} implementation does not allocateany document-specific resource, it is nonetheless a good idea to inherit from this class, as tracking missing calls to {@link java.io.Closeable#close() close()} will be easier to detect.