observeRequiredCapabilities

Takes in onCapabilitiesRequested that will be notified when image processing operations require additional data from connected Input. Right after observeRequiredCapabilities is called onCapabilitiesRequested consumer will be invoked on the caller thread with the current set of required capabilities. emptySet is used to represent that additional capabilities aren't required.

When capabilities are requested client can connect different Input which provides those capabilities, or ignore that request. In case the capabilities request is ignored some image processing functionality may not work.

It is essential to manage the returned Closeable to avoid leaking resources.