corrected a error. This error might come from a change in a new version in matlab

proxtoolbox/Problems/sudoku.py

@@ -301,7 +301,7 @@ class Sudoku(Problem):
         ax.xaxis.set_visible(False)
         ax.yaxis.set_visible(False)
         table = ax.table(cellText=self.config['sudoku'].astype(int32),loc='center')
-        for cell in table.properties()['child_artists']:
+        for cell in table.properties()['children']:
             cell.set_height(0.1)
             cell.set_width(0.1)
             txt = cell.get_text()
@@ -314,7 +314,7 @@ class Sudoku(Problem):
         ax.xaxis.set_visible(False)
         ax.yaxis.set_visible(False)
         table = ax.table(cellText=self.solution.astype(int32),loc='center')
-        for cell in table.properties()['child_artists']:
+        for cell in table.properties()['children']:
             cell.set_height(0.1)
             cell.set_width(0.1)