reactor-core/src/main/java/reactor/core/Exceptions.java
public static boolean isErrorCallbackNotImplemented(@Nullable Throwable t) {
		return t != null && t.getClass().equals(ErrorCallbackNotImplemented.class);
	}
public static boolean isErrorCallbackNotImplemented(@Nullable Throwable t) {
		return t != null && t.getClass().equals(ErrorCallbackNotImplemented.class);
	}
Check if the given error is a {@link #errorCallbackNotImplemented(Throwable) callback not implemented}
exception, in which case its {@link Throwable#getCause() cause} will be the propagated
error that couldn't be processed.

@param t the {@link Throwable} error to check
@return true if given {@link Throwable} is a callback not implemented exception.