Perhaps

```python
def _parse_body(self):
    boundary = b''.join((b'--', self.boundary))

    def body_part(part):
        fixed = MultipartDecoder._fix_first_part(x, boundary)
        return BodyPart(fixed, self.encoding)

    def test_part(part):
        return (x != b'' and x != b'\r\n' and x[:4] != b'--\r\n')

    parts = self.content.split(b''.join((b'\r\n', boundary))
    self.parts = tuple(body_part(x) for x in parts if test_part(x))
```