Faster Python - 10th version

docs/faster_python.md

@@ -37,6 +37,44 @@ print(z)
 
 ---
 
+### Code is too universal
+
+```python
+import dis
+
+def add_two_numbers(x, y):
+    return x + y
+
+
+class Foo:
+    def __init__(self, value):
+        self._value = value
+
+    def __add__(self, other):
+        return Foo(self._value + other._value)
+
+    def __str__(self):
+        return "*" * self._value
+
+
+def test_adding():
+    f1 = Foo(1)
+    f2 = Foo(2)
+
+    print(add_two_numbers(123, 456))
+    print(add_two_numbers("foo", "bar"))
+    print(add_two_numbers([1,2,3], [4,5,6]))
+    print(add_two_numbers((1,2,3), (4,5,6)))
+    print(add_two_numbers(f1, f2))
+
+
+test_adding()
+dis.dis(add_two_numbers)
+dis.dis(test_adding)
+```
+
+---
+
 ## Where's the problem?
 
 ```python