def __enter__(self) -> "_IndexWriter":
        """Enter the context introduced by the 'with' keyword

        Returns:
            _IndexWriter: The instance
        """
        self.idx_writer = open(self.idx_path, "wb")
        # fixed, vestigial practice
        self.idx_writer.write(_INDEX_HEADER)
        # fixed, vestigial practice
        self.idx_writer.write(struct.pack("<Q", 1))
        # the numeric code for the dtype
        self.idx_writer.write(struct.pack("<B", DType.code_from_dtype(self.dtype)))
        return self
Enter the context introduced by the 'with' keyword

        Returns:
            _IndexWriter: The instance
        
finetune/core/datasets/indexed_dataset.py