         case .concrete(_): return nil
         }
     }
-    
+
     // Liveness tracking for LazyTensorOperations
     //
     static func isLive(_ op: LazyTensorOperation) -> Bool {

        inputs = inputs.map { materializedAsNeeded(input: $0) }
    }

    private func materializeLiveTensors() {
        let traceInfo = LazyTensorTraceBuilder.materializationTraceInfo(self)
        debugLog("Extracted trace:\n\(traceInfo.trace)")

        let function = TFFunction(trace: traceInfo.trace)

        // Return materialized outputs if any.
        if let outputs = outputs { return outputs }

        LazyTensorOperation.materialize(targets: [self])

        // Our outputs should have been updated by now. Otherwise,
        // something terrible happened!
