Fix pres function (without unittest)

ipynb/pres030_functions.ipynb

@@ -49,12 +49,10 @@
 
 
 %% Cell type:code id: tags:
 
 ``` python
-import unittest 
-
 def add(arg0, arg1):
     """Print and return the sum of the two arguments (duck typing)."""
     result = arg0 + arg1
     print('result = ', result)
     return result
@@ -88,23 +86,20 @@
 Write a function that returns the sum of the first argument with twice the second argument.
 
 %% Cell type:code id: tags:
 
 ``` python
-import unittest
-
 def add_second_twice(arg0, arg1):
     """Return the sum of the first argument with twice the second one.
         Arguments should be of type that support sum and product by 
         an integer (e.g. numerical, string, list, ...)
         :param arg0: first argument
         :param arg1: second argument 
         :return: arg0 + 2 * arg1
     """
     pass
 
-
 ```
 
 %% Cell type:markdown id: tags:
 
 ### Do it yourself: simple function definition
@@ -124,11 +119,11 @@
     """
     result = arg0 + 2*arg1
     print(f'arg0 + 2*arg1 = {arg0} + 2*{arg1} = {result}')
     return result
 
-myfunc(4, 6)
+add_second_twice(4, 6)
 ```
 
 %%%% Output: execute_result
 
     16
@@ -137,14 +132,10 @@
 
 ``` python
 myfunc('a', 'b')
 ```
 
-%%%% Output: execute_result
-
-    'abb'
-
 %% Cell type:markdown id: tags:
 
 ## Is the function correct ? 
 
 - What does it means **correct** ?