Ajout de docstrings

functions.py

@@ -1,7 +1,17 @@
 def is_even(n):
+    """Returns True if n is even.
+
+    >>> is_even(10)
+    True
+    """
     return n % 2 == 0
 
 def is_odd(n):
+    """Returns True if n is odd.
+
+    >>> is_odd(10)
+    False
+    """
     return not is_even(n)
 
 for i in range(10):