[Replace] Add case when replacing a graph by a Producer + add debug log.

src/graph/GraphView.cpp

@@ -1256,6 +1256,7 @@ bool Aidge::GraphView::replace(const std::shared_ptr<GraphView>& oldGraph, const
         for (const auto& nodePtr : newNodes) {
             nodePtr->removeView(newGraph);
         }
+        Log::warn("Discrepancy between the number of input/output of the graph to replace.\n\t- OLD NB INPUTS: {} - NEW NB INPUTS {}\n\t- OLD NB OUTPUTS: {} - NEW NB OUTPUTS {}", oldOIn.size(), newOIn.size(), oldOOut.size(), newOOut.size());
         return false;
     }
 
@@ -1325,14 +1326,27 @@ bool Aidge::GraphView::replace(const std::shared_ptr<GraphView>& oldGraph, const
                     newOOut[o].first -> addChild(child.first, newOOut[o].second, child.second);
                 }
             }
-        }
-        else {
+        } else if ( // for folding case
+          ((newOIn.size() == 0)) &&
+          ((oldOOut.size() == newOOut.size()) && (newOOut.size() == 1))
+        ) {
+            // Case 4
+            // Replace any nodes by a Producer
+            // No need to remove old inputs it is removed later on ...
+            for (std::size_t o = 0; o < oldOOut.size(); ++o) {
+                for (const auto& child : outputChildren[o]) {
+                    newOOut[o].first -> addChild(child.first, newOOut[o].second, child.second);
+                }
+            }
+
+        } else {
             for (const auto& nodePtr : oldNodes) {
                 nodePtr->removeView(oldGraph);
             }
             for (const auto& nodePtr : newNodes) {
                 nodePtr->removeView(newGraph);
             }
+            Log::warn("Could not replace");
             return false;
         }
     }