{!./src/dependencies/tutorial006.py!}
```
+In this case, this `__call__` is what **FastAPI** will use to check for additional parameters and sub-dependencies, and this is what will be called to pass a value to the parameter in your *path operation function* later.
+
## Parameterize the instance
And now, we can use `__init__` to declare the parameters of the instance that we can use to "parameterize" the dependency:
But then we get a `dict` in the parameter `commons` of the path operation function.
-And we know that `dict`s can't provide a lot of editor support because they can't know their keys and value types.
+And we know that editors can't provide a lot of support (like completion) for `dict`s, because they can't know their keys and value types.
We can do better...
A "**callable**" in Python is anything that Python can "call" like a function.
-So, if you have an object `something` (that might _not_ be a function) and you can do:
+So, if you have an object `something` (that might _not_ be a function) and you can "call" it (execute it) like:
```Python
something()
You might notice that to create an instance of a Python class, you use that same syntax.
+For example:
+
+```Python
+class Cat:
+ def __init__(self, name: str):
+ self.name = name
+
+
+fluffy = Cat(name="Mr Fluffy")
+```
+
+In this case, `fluffy` is an instance of the class `Cat`.
+
+And to create `fluffy`, you are "calling" `Cat`.
+
So, a Python class is also a **callable**.
Then, in **FastAPI**, you could use a Python class as a dependency.
If you pass a "callable" as a dependency in **FastAPI**, it will analyze the parameters for that "callable", and process them in the same way as the parameters for a path operation function. Including sub-dependencies.
-That also applies to callables with no parameters at all. The same as would be for path operation functions with no parameters.
+That also applies to callables with no parameters at all. The same as it would be for path operation functions with no parameters.
Then, we can change the dependency "dependable" `common_parameters` from above to the class `CommonQueryParameters`: