diff --git a/Pipfile b/Pipfile
index 898df0d..290df6b 100644
--- a/Pipfile
+++ b/Pipfile
@@ -10,4 +10,4 @@ graphviz = "*"
 [dev-packages]
 
 [requires]
-python_version = "3.8"
+python_version = "3.9"
diff --git a/Pipfile.lock b/Pipfile.lock
index fb6cb46..e9f2122 100644
--- a/Pipfile.lock
+++ b/Pipfile.lock
@@ -1,11 +1,11 @@
 {
     "_meta": {
         "hash": {
-            "sha256": "c316715bdcade179f443832fe51c6ec5b863aed04f6dadd5a25fc36efe877089"
+            "sha256": "6a6221941c907af6c963dda01292c00cc04123ccc5f1cb59a556961d006b832f"
         },
         "pipfile-spec": 6,
         "requires": {
-            "python_version": "3.8"
+            "python_version": "3.9"
         },
         "sources": [
             {
@@ -18,17 +18,18 @@
     "default": {
         "certifi": {
             "hashes": [
-                "sha256:1d987a998c75633c40847cc966fcf5904906c920a7f17ef374f5aa4282abd304",
-                "sha256:51fcb31174be6e6664c5f69e3e1691a2d72a1a12e90f872cbdb1567eb47b6519"
+                "sha256:1a4995114262bffbc2413b159f2a1a480c969de6e6eb13ee966d470af86af59c",
+                "sha256:719a74fb9e33b9bd44cc7f3a8d94bc35e4049deebe19ba7d8e108280cfd59830"
             ],
-            "version": "==2020.4.5.1"
+            "version": "==2020.12.5"
         },
         "chardet": {
             "hashes": [
-                "sha256:84ab92ed1c4d4f16916e05906b6b75a6c0fb5db821cc65e70cbd64a3e2a5eaae",
-                "sha256:fc323ffcaeaed0e0a02bf4d117757b98aed530d9ed4531e3e15460124c106691"
+                "sha256:0d6f53a15db4120f2b08c94f11e7d93d2c911ee118b6b30a04ec3ee8310179fa",
+                "sha256:f864054d66fd9118f2e67044ac8981a54775ec5b67aed0441892edb553d21da5"
             ],
-            "version": "==3.0.4"
+            "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'",
+            "version": "==4.0.0"
         },
         "docker": {
             "hashes": [
@@ -47,27 +48,27 @@
         },
         "graphviz": {
             "hashes": [
-                "sha256:cb0e878f90378489f17aab140b68e64e44b79e4cb59a530c8863d84bf2e2e5f5",
-                "sha256:e104ba036c8aef84320ec80560e544cd3cad68c9f90394b4e2b87bc44ab09791"
+                "sha256:3cad5517c961090dfc679df6402a57de62d97703e2880a1a46147bb0dc1639eb",
+                "sha256:d2d25af1c199cad567ce4806f0449cb74eb30cf451fd7597251e1da099ac6e57"
             ],
             "index": "pypi",
-            "version": "==0.14"
+            "version": "==0.16"
         },
         "idna": {
             "hashes": [
-                "sha256:7588d1c14ae4c77d74036e8c22ff447b26d0fde8f007354fd48a7814db15b7cb",
-                "sha256:a068a21ceac8a4d63dbfd964670474107f541babbd2250d61922f029858365fa"
+                "sha256:b307872f855b18632ce0c21c5e45be78c0ea7ae4c15c828c20788b26921eb3f6",
+                "sha256:b97d804b1e9b523befed77c48dacec60e6dcb0b5391d57af6a65a312a90648c0"
             ],
             "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3'",
-            "version": "==2.9"
+            "version": "==2.10"
         },
         "requests": {
             "hashes": [
-                "sha256:43999036bfa82904b6af1d99e4882b560e5e2c68e5c4b0aa03b655f3d7d73fee",
-                "sha256:b3f43d496c6daba4493e7c431722aeb7dbc6288f52a6e04e7b6023b0247817e6"
+                "sha256:27973dd4a904a4f13b263a19c866c13b92a39ed1c964655f025f3f8d3d75b804",
+                "sha256:c210084e36a42ae6b9219e00e48287def368a26d03a048ddad7bfee44f75871e"
             ],
             "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4'",
-            "version": "==2.23.0"
+            "version": "==2.25.1"
         },
         "six": {
             "hashes": [
@@ -79,18 +80,19 @@
         },
         "urllib3": {
             "hashes": [
-                "sha256:3018294ebefce6572a474f0604c2021e33b3fd8006ecd11d62107a5d2a963527",
-                "sha256:88206b0eb87e6d677d424843ac5209e3fb9d0190d0ee169599165ec25e9d9115"
+                "sha256:2f4da4594db7e1e110a944bb1b551fdf4e6c136ad42e4234131391e21eb5b0df",
+                "sha256:e7b021f7241115872f92f43c6508082facffbd1c048e3c6e2bb9c2a157e28937"
             ],
             "markers": "python_version >= '2.7' and python_version not in '3.0, 3.1, 3.2, 3.3, 3.4' and python_version < '4'",
-            "version": "==1.25.9"
+            "version": "==1.26.4"
         },
         "websocket-client": {
             "hashes": [
-                "sha256:0fc45c961324d79c781bab301359d5a1b00b13ad1b10415a4780229ef71a5549",
-                "sha256:d735b91d6d1692a6a181f2a8c9e0238e5f6373356f561bb9dc4c7af36f452010"
+                "sha256:44b5df8f08c74c3d82d28100fdc81f4536809ce98a17f0757557813275fbb663",
+                "sha256:63509b41d158ae5b7f67eb4ad20fecbb4eee99434e73e140354dc3ff8e09716f"
             ],
-            "version": "==0.57.0"
+            "markers": "python_version >= '2.6' and python_version not in '3.0, 3.1, 3.2, 3.3'",
+            "version": "==0.58.0"
         }
     },
     "develop": {}
diff --git a/requirements-dev.txt b/requirements-dev.txt
deleted file mode 100644
index 560d405..0000000
--- a/requirements-dev.txt
+++ /dev/null
@@ -1,2 +0,0 @@
-docker-py
-graphviz