This line (and the similar line below) is dodgy, because you are creating a mutable value and using it as the default value for a keyword argument. In Python, default values for keyword arguments are evaluated when the `def` form is evaluated, not when the function is called. This means that only one dictionary gets created, and it is used as the default value for the `template_context` in all calls to this `__init__` method (and thus to the `template_context` attribute of all objects of this class). This means that if any code updates this dictionary, the update gets propagated to all future objects of this class.

(It looks harmless enough here, since code is unlikely to construct an object and then update its `template_context` attribute: callers will pass in their own `template_context` dictionaries. But still worth replacing `{}` with `None` and then writing
```
self.template_context = template_context or {}
```
so that people reading the code don't have to worry about whether there's a real problem here.)