@Nonnull
	private Set<String> getDirectChildren(@Nonnull String parent) {
		return parentToChild.getOrDefault(parent, Collections.emptySet());
	}
@param parent
		Parent to find children of.

@return Direct extensions/implementations of the given parent.
recaf-core/src/main/java/software/coley/recaf/services/inheritance/InheritanceGraph.java