Solution

app/main.py

@@ -1,21 +1,3 @@
 def count_occurrences(phrase: str, letter: str) -> int:
-    """
-    Implement count_occurrences function:
-
-    It takes a phrase and a letter and calculates the number of times
-    the letter appears in the phrase. The function is case insensitive.
-
-    count_occurrences("letter", "t") == 2
-    count_occurrences("abc", "a") == 1
-    count_occurrences("abc", "d") == 0
-    count_occurrences("ABC", "a") == 1
-
-    :param phrase: phrase to count in it
-    :param letter: letter to find occurrences of it
-    :return: count occurrences of letter in phrase
-    """
-    counter = 0
-    for i in range(len(phrase)):
-        if phrase[i].lower() in letter.lower():
-            counter += 1
-    return counter
+    return sum([1 for i in range(len(phrase))
+                if phrase[i].lower() == letter.lower()])