async downloadToFile(filePath, offset = 0, count, options = {}) {
        return tracingClient.withSpan("BlobClient-downloadToFile", options, async (updatedOptions) => {
            const response = await this.download(offset, count, Object.assign(Object.assign({}, options), { tracingOptions: updatedOptions.tracingOptions }));
            if (response.readableStreamBody) {
                await readStreamToLocalFile(response.readableStreamBody, filePath);
            }
            // The stream is no longer accessible so setting it to undefined.
            response.blobDownloadStream = undefined;
            return response;
        });
    }
ONLY AVAILABLE IN NODE.JS RUNTIME.

Downloads an Azure Blob to a local file.
Fails if the the given file path already exits.
Offset and count are optional, pass 0 and undefined respectively to download the entire blob.

@param filePath -
@param offset - From which position of the block blob to download.
@param count - How much data to be downloaded. Will download to the end when passing undefined.
@param options - Options to Blob download options.
@returns The response data for blob download operation,
                                                but with readableStreamBody set to undefined since its
                                                content is already read and written into a local file
                                                at the specified path.