protected InterceptedStream<T> closeInterceptedStream(String index) {
        return streams.close(index);
    }
Closes the stream having the given index and currently being intercepted
by this filter, if any. If no such stream is being intercepted, then this
function has no effect.

@param index
    The index of the stream to close.

@return
    The stream associated with the given index, if the stream is being
    intercepted, or null if no such stream exists.
guacamole/src/main/java/org/apache/guacamole/tunnel/StreamInterceptingFilter.java