public int size() {
        return definitionsByName.size();
    }
Makes data available for decoding for the given hit.

@param summaryClass the requested summary class
@param data docsum data from backend
@param hit the Hit corresponding to this document summary
@return Error message or null on success.
@throws ConfigurationException if the summary class of this hit is missing
container-search/src/main/java/com/yahoo/prelude/fastsearch/DocsumDefinitionSet.java