Maintenance: Adjust formatter to catch listcomp

**Example:** https://github.com/awslabs/aws-lambda-powertools-python/pull/255#issuecomment-758766407

**Actual**

```python
return [self._parse(data=record.Sns.Message, model=model) for record in parsed_envelope.Records]
```

**Expected**

```python
return [
    self._parse(data=record.Sns.Message, model=model) 
    for record in parsed_envelope.Records
]
```