Parse stream to find a given byte string.

def _parse(self, stream, context, path):
        """Parse stream to find a given byte string."""
        start = stream.tell()
        read_bytes = ""
        if self.max_length:
            read_bytes = stream.read(self.max_length)
        else:
            read_bytes = stream.read()
        skip = read_bytes.find(self.find) + len(self.find)
        stream.seek(start + skip)
        return skip