diff --git a/Pipfile b/Pipfile
index 913a25a..158c835 100644
--- a/Pipfile
+++ b/Pipfile
@@ -8,6 +8,7 @@ verify_ssl = true
 [packages]
 numpy = "*"
 jupyter = "*"
+graphviz = "*"
 
 [requires]
 python_version = "3.7"
diff --git a/Pipfile.lock b/Pipfile.lock
index 363eb53..1794f07 100644
--- a/Pipfile.lock
+++ b/Pipfile.lock
@@ -1,7 +1,7 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "f1d4a261bb7cfa392e1636fb86bb032c413b9219625811d2f102d265715c2424"
+            "sha256": "0c5e02cf500506f5ef817e280e5ad2f6a277d059e0b36854d96db66d0dd550b2"
         },
         "pipfile-spec": 6,
         "requires": {
@@ -121,11 +121,11 @@
         },
         "defusedxml": {
             "hashes": [
-                "sha256:6687150770438374ab581bb7a1b327a847dd9c5749e396102de3fad4e8a3ef93",
-                "sha256:f684034d135af4c6cbb949b8a4d2ed61634515257a67299e5f940fbaa34377f5"
+                "sha256:1bb3032db185915b62d7c6209c5a8792be6a32ab2fedacc84e01b52c51aa3e69",
+                "sha256:a352e7e428770286cc899e2542b6cdaedb2b4953ff269a210103ec58f6198a61"
             ],
             "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'",
-            "version": "==0.6.0"
+            "version": "==0.7.1"
         },
         "entrypoints": {
             "hashes": [
@@ -135,6 +135,14 @@
             "markers": "python_version >= '2.7'",
             "version": "==0.3"
         },
+        "graphviz": {
+            "hashes": [
+                "sha256:3cad5517c961090dfc679df6402a57de62d97703e2880a1a46147bb0dc1639eb",
+                "sha256:d2d25af1c199cad567ce4806f0449cb74eb30cf451fd7597251e1da099ac6e57"
+            ],
+            "index": "pypi",
+            "version": "==0.16"
+        },
         "ipykernel": {
             "hashes": [
                 "sha256:98321abefdf0505fb3dc7601f60fc4087364d394bd8fad53107eb1adee9ff475",
@@ -145,11 +153,11 @@
         },
         "ipython": {
             "hashes": [
-                "sha256:1918dea4bfdc5d1a830fcfce9a710d1d809cbed123e85eab0539259cb0f56640",
-                "sha256:1923af00820a8cf58e91d56b89efc59780a6e81363b94464a0f17c039dffff9e"
+                "sha256:04323f72d5b85b606330b6d7e2dc8d2683ad46c3905e955aa96ecc7a99388e70",
+                "sha256:34207ffb2f653bced2bc8e3756c1db86e7d93e44ed049daae9814fed66d408ec"
             ],
             "markers": "python_version >= '3.3'",
-            "version": "==7.20.0"
+            "version": "==7.21.0"
         },
         "ipython-genutils": {
             "hashes": [
@@ -199,11 +207,11 @@
         },
         "jupyter-client": {
             "hashes": [
-                "sha256:5eaaa41df449167ebba5e1cf6ca9b31f7fd4f71625069836e2e4fee07fe3cb13",
-                "sha256:649ca3aca1e28f27d73ef15868a7c7f10d6e70f761514582accec3ca6bb13085"
+                "sha256:c4bca1d0846186ca8be97f4d2fa6d2bae889cce4892a167ffa1ba6bd1f73e782",
+                "sha256:e053a2c44b6fa597feebe2b3ecb5eea3e03d1d91cc94351a52931ee1426aecfc"
             ],
             "markers": "python_version >= '3.5'",
-            "version": "==6.1.11"
+            "version": "==6.1.12"
         },
         "jupyter-console": {
             "hashes": [
@@ -303,11 +311,11 @@
         },
         "nbclient": {
             "hashes": [
-                "sha256:0ed6e5700ad18818030a3a5f0f201408c5972d8e38793840cd9339488fd9f7c4",
-                "sha256:1e0375490cd33fda6c23e61084476298a87f34d02607a038aa8ecc6e8901615f"
+                "sha256:db17271330c68c8c88d46d72349e24c147bb6f34ec82d8481a8f025c4d26589c",
+                "sha256:e79437364a2376892b3f46bedbf9b444e5396cfb1bc366a472c37b48e9551500"
             ],
             "markers": "python_full_version >= '3.6.1'",
-            "version": "==0.5.2"
+            "version": "==0.5.3"
         },
         "nbconvert": {
             "hashes": [
@@ -417,11 +425,11 @@
         },
         "prompt-toolkit": {
             "hashes": [
-                "sha256:0fa02fa80363844a4ab4b8d6891f62dd0645ba672723130423ca4037b80c1974",
-                "sha256:62c811e46bd09130fb11ab759012a4ae385ce4fb2073442d1898867a824183bd"
+                "sha256:4cea7d09e46723885cb8bc54678175453e5071e9449821dce6f017b1d1fbfc1a",
+                "sha256:9397a7162cf45449147ad6042fa37983a081b8a73363a5253dd4072666333137"
             ],
             "markers": "python_full_version >= '3.6.1'",
-            "version": "==3.0.16"
+            "version": "==3.0.17"
         },
         "ptyprocess": {
             "hashes": [
@@ -441,11 +449,11 @@
         },
         "pygments": {
             "hashes": [
-                "sha256:37a13ba168a02ac54cc5891a42b1caec333e59b66addb7fa633ea8a6d73445c0",
-                "sha256:b21b072d0ccdf29297a82a2363359d99623597b8a265b8081760e4d0f7153c88"
+                "sha256:2656e1a6edcdabf4275f9a3640db59fd5de107d88e8663c5d4e9a0fa62f77f94",
+                "sha256:534ef71d539ae97d4c3a4cf7d6f110f214b0e687e92f9cb9d2a3b0d3101289c8"
             ],
             "markers": "python_version >= '3.5'",
-            "version": "==2.8.0"
+            "version": "==2.8.1"
         },
         "pyparsing": {
             "hashes": [