[Bug] Caching is not unique for classes with call function

For example 
```python
class Test:
    def __call__(self, a, b):
        return a+b
```
While the class definition is unique the instance `Test()` is not this results in a different hash and consequently the calculation is repeated rather than reloaded. So at the moment it is not recommended to use dynamically defined objects in combination with the caching feature. 