move show_dag method to sepate plugin

lb/graph.py

@@ -274,17 +274,6 @@ def create_edge(block_from, value_from, block_dest, value_dest):
         self.vertices = vertices
         self.entry_points = entry_points
 
-    def show_dag(self):
-        for v in self.vertices.values():
-            print(v.fields['name'])
-            print(' from:')
-            for prev in v.prev_vertices:
-                print('  {} -> {}'.format(prev.block_from.fields['name'], prev.value_from))
-            print(' to:')
-            for to in v.next_vertices:
-                print('  {} -> {}'.format(to.block_dest.fields['name'], to.value_dest))
-            print('____________________')
-
     def _check_yaml(self):
         """
         Checks that the YAML file is correctly typed.

lb/plugins/show_dag.py

@@ -0,0 +1,32 @@
+# Copyright 2017 The Lambda-blocks developers. See AUTHORS for details.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""
+This plugin allows for a very basic representation of the graph,
+showing for each vertice its inner and outer links.
+"""
+
+from lb.plugins_manager import before_graph_execution
+
+@before_graph_execution
+def show_dag(vertices, entry_points):
+    for v in vertices.values():
+        print(v.fields['name'])
+        print(' from:')
+        for prev in v.prev_vertices:
+            print('  {} -> {}'.format(prev.block_from.fields['name'], prev.value_from))
+        print(' to:')
+        for to in v.next_vertices:
+            print('  {} -> {}'.format(to.block_dest.fields['name'], to.value_dest))
+        print('____________________')