feat: start enum val with buffer, count from top

It is good to have buffers between enum values.
And start counting from the "top of the hierarchy" value,
the Director, to the bottom because it is unlikely that a
lot of values will be added on top of the Director.

solutions/object_oriented_design/call_center/call_center.ipynb

@@ -69,9 +69,9 @@
     "\n",
     "class Rank(Enum):\n",
     "\n",
-    "    OPERATOR = 0\n",
+    "    OPERATOR = 30\n",
-    "    SUPERVISOR = 1\n",
+    "    SUPERVISOR = 20\n",
-    "    DIRECTOR = 2\n",
+    "    DIRECTOR = 10\n",
     "\n",
     "\n",
     "class Employee(metaclass=ABCMeta):\n",

solutions/object_oriented_design/call_center/call_center.py

@@ -5,10 +5,9 @@ from enum import Enum
 
 class Rank(Enum):
 
-    OPERATOR = 0
+    OPERATOR = 30
-    SUPERVISOR = 1
+    SUPERVISOR = 20
-    DIRECTOR = 2
+    DIRECTOR = 10
-
 
 class Employee(metaclass=ABCMeta):