def staged_trace(trace_id)
      candidate = nil
      @staging_lock.synchronize {
        @staging_queue.each do |trace|
          if trace.id == trace_id
            candidate = trace
            break
          end
        end
      }
      unless candidate
        ::Instana.logger.debug("Couldn't find staged trace with trace_id: #{trace_id}")
      end
      candidate
    end
def staged_trace(trace_id)
      candidate = nil
      @staging_lock.synchronize {
        @staging_queue.each do |trace|
          if trace.id == trace_id
            candidate = trace
            break
          end
        end
      }
      unless candidate
        ::Instana.logger.debug("Couldn't find staged trace with trace_id: #{trace_id}")
      end
      candidate
    end
Retrieves a single staged trace from the staging queue.  Staged traces
 are traces that have completed but may have outstanding
 asynchronous spans.

 @param trace_id [Integer] the Trace ID to be searched for