remove old test data, intro check

examples/Introduction.ipynb

@@ -446,7 +446,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<graphviz.graphs.Digraph at 0x7fba1600e6e0>"
+       "<graphviz.graphs.Digraph at 0x7f8e493abc40>"
       ]
      },
      "execution_count": 7,
@@ -1944,7 +1944,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<graphviz.graphs.Digraph at 0x7fba15fae860>"
+       "<graphviz.graphs.Digraph at 0x7f8e491c2d40>"
       ]
      },
      "execution_count": 39,
@@ -2228,7 +2228,7 @@
        "</svg>\n"
       ],
       "text/plain": [
-       "<graphviz.graphs.Digraph at 0x7fba15fef310>"
+       "<graphviz.graphs.Digraph at 0x7f8e491c1120>"
       ]
      },
      "execution_count": 40,