add iterate_f function and associated test func

testing_project/logistic.py

@@ -2,3 +2,10 @@
 
 def f(x, r):
     return r * x * (1-x) 
+
+def iterate_f(it, x, r):
+    result = [x]
+    for i in range(it):
+        x = f(x, r)
+        result.append(x)
+    return result