Split tuple at commas first

Ours:
```python
def f():
    return self.get_filename() + ".csv", "text/csv", output.getvalue().encode(
        "utf-8----------------"
    )
```
Black:
```python
def f():
    return (
        self.get_filename() + ".csv",
        "text/csv",
        output.getvalue().encode("utf-8----------------"),
    )
```