return None
```

...calling the path `/items/invalidnone` will raise an error, because `None` is not a valid type for the `response_model` declared with `Item`.

You could also be implicitly returning `None` without realizing, for example:

```Python
from fastapi import FastAPI
from pydantic import BaseModel

class Item(BaseModel):
    name: str
    price: Optional[float] = None

### Node Binaries

filename | sha512 hash
-------- | -----------
[kubernetes-node-linux-amd64.tar.gz](https://dl.k8s.io/v1.19.16/kubernetes-node-linux-amd64.tar.gz) | fa3a29eae5e047ec99049a789d4793e05bdbdc9a31c0216a20cb60bc7aada2750d90bdfc6746e04d77e84390d2149a68f466aab4222e32dcf50ffb527e4c97e1

1D15E         ; mapped                 ; 1D157 1D165   # 3.1  MUSICAL SYMBOL HALF NOTE
1D15F         ; mapped                 ; 1D158 1D165   # 3.1  MUSICAL SYMBOL QUARTER NOTE
1D160         ; mapped                 ; 1D158 1D165 1D16E #3.1 MUSICAL SYMBOL EIGHTH NOTE
1D161         ; mapped                 ; 1D158 1D165 1D16F #3.1 MUSICAL SYMBOL SIXTEENTH NOTE

font-family: inherit;\n  font-size: inherit;\n  line-height: inherit;\n}\n\nbutton,\nselect {\n  text-transform: none;\n}\n\n[role=button] {\n  cursor: pointer;\n}\n\nselect {\n  word-wrap: normal;\n}\nselect:disabled {\n  opacity: 1;\n}\n\n[list]:not([type=date]):not([type=datetime-local]):not([type=month]):not([type=week]):not([type=time])::-webkit-calendar-picker-indicator {\n  display: none !important;\n}\n\nbutton,\n[type=button],\n[type=reset],\n[type=submit] {\n  -webkit-appearance: button;\n}...

font-family: -apple-system, BlinkMacSystemFont, \"Segoe UI\", Roboto, \"Helvetica Neue\", Arial, \"Noto Sans\", \"Liberation Sans\", sans-serif, \"Apple Color Emoji\", \"Segoe UI Emoji\", \"Segoe UI Symbol\", \"Noto Color Emoji\";\n  font-style: normal;\n  font-weight: 400;\n  line-height: 1.5;\n  text-align: left;\n  text-align: start;\n  text-decoration: none;\n  text-shadow: none;\n  text-transform: none;\n  letter-spacing: normal;\n  word-break: normal;\n  white-space: normal;\n  word-spacing: normal;\n...

     * @return The value of found property. (NotNull: if not found, exception)
     * @throws ConfigPropertyNotFoundException When the property is not found.
     */
    String get(String propertyKey);

    /**
     * Is the property true?
     * @param propertyKey The key of the property which is boolean type. (NotNull)
     * @return The determination, true or false. (if not found, exception)