public final FlatDataCollection put(Object key, FlatDataCollection value) {
        return internalData.put(key, value);
    }
public final FlatDataCollection put ( Object key , FlatDataCollection value ) { return internalData . put ( key , value ) ; }
Adds a particular key-value into the internal map. It returns the previous
value which was associated with that key.

@param key
@param value
@return