Implement py-count-occurrences

app/main.py

@@ -1,3 +1,13 @@
 def count_occurrences(phrase: str, letter: str) -> int:
-    # write your code here
-    pass
+    """
+        Count occurrences of a letter in a phrase (case insensitive).
+
+        Parameters:
+            phrase (str): The string in which to search for the letter.
+            letter (str): The letter to count within the phrase.
+
+        Returns:
+            int: The number of occurrences of the letter in the phrase.
+        """
+    string_lower = phrase.lower()
+    return string_lower.count(letter.lower())