[Add] GraphView helper for manipulation functions, add 'producers()'

include/aidge/recipies/GraphViewHelper.hpp

+/********************************************************************************
+ * Copyright (c) 2023 CEA-List
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ ********************************************************************************/
+
+#ifndef AIDGE_CORE_UTILS_RECIPIES_H_
+#define AIDGE_CORE_UTILS_RECIPIES_H_
+
+#include <memory>
+#include <set>
+
+#include "aidge/graph/Node.hpp"
+#include "aidge/graph/GraphView.hpp"
+
+
+namespace Aidge {
+
+/**
+ * @brief Getter for every Producer operator in a GraphView.
+ * @param graphview GraphView instance where Producers should be searched.
+ * @return std::set<std::shared_ptr<Node>>
+ */
+std::set<std::shared_ptr<Aidge::Node>> producers(std::shared_ptr<Aidge::GraphView> graphview) {
+    std::set<std::shared_ptr<Node>> res;
+    const std::set<std::shared_ptr<Node>> nodes = graphview->getNodes();
+
+    std::copy_if(nodes.cbegin(),
+                    nodes.cend(),
+                    std::inserter(res, res.begin()),
+                    [](std::shared_ptr<Node> n){ return n->type() == "Producer"; });
+
+    return res;
+}
+} // namespace Aidge
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