Adding docstring for commonality

puzzles/day03.py

@@ -88,7 +88,20 @@ class Diagnostics:
         return oxygen_generator_rating * co2_scrubber_rating
 
     @staticmethod
-    def commonality(report: List[int]) -> List[Dict[str, int]]:
+    def commonality(report: List[int]) -> List[int]:
+        """
+        Return the most common value in each column of binary numbers
+
+        Args:
+            report: List of binary numbers
+
+        Returns:
+            List containing the most common value in the column
+            Possible Values:
+                0
+                1
+                2 - This indicates equally common
+        """
         num_1 = defaultdict(int)
         for binary in report:
             for column, bit in enumerate(binary):