question: public TraceScope newScope ( String description ) { TraceScope parentScope = threadLocalScope . get ( ) ; ThreadContext context = threadContext . get ( ) ; if ( parentScope != null ) { return newScopeImpl ( context , description , parentScope ) ; } if ( ! context . isTopLevel ( ) ) { context . pushScope ( ) ; return nullScope ; } if ( ! sample ( ) ) { context . pushScope ( ) ; return nullScope ; } return newScopeImpl ( context , description ) ; }
target:  Create a new trace scope. If there are no scopes above the current scope, we will apply our configured samplers. Otherwise, we will create a trace Span only if this thread is already tracing.