A node in a type hierarchy graph. The "key" is used to facilitate matching
and storing. The value is the original label used for the type. There are two
special cases -- both top and bottom are fixed and never keyed.
Returns the entire set of values for this particular node.
public void addValue(String value)
If the value is not already one of the type labels represented in this
node, then it's added. This has no effect on the already existing key. If
the matching rules were not obeyed, then erroneous values are fair game,
since the node itself doesn't know the matching rules used to create it.
public String toString()
toString in class Object
public String toString(boolean deep)
deep - Whether to list parent and child nodes recursively or not
a human-readable text version of what's in the node