List the terms that are obsolete

## Working with obsolete terms

1. Get all the obsolete terms in a given ontology.

1. Get all the obsolete terms in a given ontology:

       			use OBO::Parser::OBOParser;

       			my $my_parser = OBO::Parser::OBOParser->new();
       			my $ontology = $my_parser->work("my_obo_ontology.obo");

       			foreach my $term (@{$ontology->get_terms()}) {
       				print $term->id(), "\t", $term->def()->text(), "\n" if (defined $term->id() && $term->def()->text() && $term->is_obsolete());
       			}