Solution

app/cafe.py

@@ -0,0 +1,28 @@
+import datetime
+from app.errors import (
+    VaccineError,
+    NotVaccinatedError,
+    OutdatedVaccineError,
+    NotWearingMaskError
+)
+
+
+class Cafe:
+    def __init__(self, name: str) -> None:
+        self.name = name
+
+    def visit_cafe(
+            self,
+            visitor: dict
+    ) -> VaccineError | NotWearingMaskError | str:
+
+        if "vaccine" not in visitor:
+            raise NotVaccinatedError("This visitor is no vaccinated!")
+
+        if visitor["vaccine"]["expiration_date"] < datetime.date.today():
+            raise OutdatedVaccineError("This visitor has expired vaccine!")
+
+        if visitor["wearing_a_mask"] is False:
+            raise NotWearingMaskError("This visitor doesn't have a mask!")
+
+        return f"Welcome to {self.name}"

app/errors.py

@@ -0,0 +1,14 @@
+class VaccineError(Exception):
+    pass
+
+
+class NotVaccinatedError(VaccineError):
+    pass
+
+
+class OutdatedVaccineError(VaccineError):
+    pass
+
+
+class NotWearingMaskError(Exception):
+    pass

app/main.py

@@ -1 +1,24 @@
-# write your code here
+from app.errors import (
+    VaccineError,
+    NotWearingMaskError
+)
+from app.cafe import Cafe
+
+
+def go_to_cafe(friends: list, cafe: Cafe) -> str:
+    masks_to_buy = 0
+
+    for friend in friends:
+        try:
+            cafe.visit_cafe(friend)
+
+        except VaccineError:
+            return "All friends should be vaccinated"
+
+        except NotWearingMaskError:
+            masks_to_buy += 1
+
+    if masks_to_buy > 0:
+        return f"Friends should buy {masks_to_buy} masks"
+
+    return f"Friends can go to {cafe.name}"