Fixed missing import

Author: kmvanbrunt

examples/basic_completion.py

@@ -11,6 +11,8 @@
 familiar with argparse. The recommended approach for tab completing positional tokens and flags is to use
 argparse-based completion. For an example integrating tab completion with argparse, see argparse_completion.py
 """
+import functools
+
 import cmd2
 
 # List of strings used with completion functions