elk-reasoner/src/main/java/org/semanticweb/elk/reasoner/stages/ClassTaxonomyState.java
private int pruneToRemove() {
		final Iterator<IndexedClass> iter = toRemove_.iterator();
		int size = 0;
		while (iter.hasNext()) {
			final IndexedClass cls = iter.next();
			/* @formatter:off
			 * 
			 * Should be pruned when
			 * it is not in taxonomy, or
			 * it is in the bottom class.
			 * 
			 * @formatter:on
			 */
			final TaxonomyNode<ElkClass> node = taxonomy_
					.getNode(cls.getElkEntity());
			if (node == null) {
				iter.remove();
				continue;
			}
			// else
			if (cls == ontologyIndex_.getOwlNothing()) {
				iter.remove();
				continue;
			}
			size++;
		}
		return size;
	}
private int pruneToRemove() {
		final Iterator<IndexedClass> iter = toRemove_.iterator();
		int size = 0;
		while (iter.hasNext()) {
			final IndexedClass cls = iter.next();
			/* @formatter:off
			 * 
			 * Should be pruned when
			 * it is not in taxonomy, or
			 * it is in the bottom class.
			 * 
			 * @formatter:on
			 */
			final TaxonomyNode<ElkClass> node = taxonomy_
					.getNode(cls.getElkEntity());
			if (node == null) {
				iter.remove();
				continue;
			}
			// else
			if (cls == ontologyIndex_.getOwlNothing()) {
				iter.remove();
				continue;
			}
			size++;
		}
		return size;
	}
Prunes {@link #toRemove_}.
<p>
<strong>{@code taxonomy_} must not be {@code null}!</strong>

@return The resulting size of {@link #toRemove_}.