Implemented function to count people

Honestly I don't like this lesson on dictionaries! This is a perfect use
case for object-oriented programming; dictionaries are just lookup
tables. I think it makes more sense to teach dicts in the context of
price lookups, or passwords, or something that has more structure
than just a place to put names variables.

friend_functions.py

@@ -9,7 +9,7 @@
 # Your job is to complete these functions. Remove the NotImplementedError from
 # each and instead write code which returns the expected values. 
 
-def count_people(people):
+def count_people(people: dict):
     """Counts the number of people. 
     
         >>> count_people(family)
@@ -17,7 +17,7 @@ def count_people(people):
         >>> count_people(friends)
         10
     """
-    raise NotImplementedError()
+    return len(people)
 
 def get_email(people, name):
     """Returns the named person's email address. If there is no such person, returns None.