</li>
</ol>

<h3 id="If_statements">If statements</h3>

<p>
"If" statements specify the conditional execution of two branches
according to the value of a boolean expression.  If the expression
evaluates to true, the "if" branch is executed, otherwise, if
present, the "else" branch is executed.
</p>

<pre class="ebnf">

app = FastAPI()

@app.get("/items/invalidnone", response_model=Item)
def get_invalid_none():
    if flag:
        return {"name": "foo"}
    # if flag is False, at this point the function will implicitly return None
```

If you have *path operations* using `response_model` that need to be allowed to return `None`, make it explicit in `response_model` using `Union[Something, None]`: