public abstract class MetaContentProvider
According to the:
if a node of a certain type makes a keyref to a topic ref on which is defined, the content of the key
will be extracted from that particular .
This content will appear inline in the Author page for that particular keyref.
It will also appear in the documentation window when the value for a keyref is computed.
The API will get called by Oxygen either when the content completion shows the user descriptions for each key reference
or when the content of a keyref is shown as static text in the editor.