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let abort: ( WebAPI.FileAPI.fileSystemWritableFileStream, ~reason: JSON.t=?,) => Promise.t<unit>
let asWritableStream: WebAPI.FileAPI.fileSystemWritableFileStream => WebAPI.FileAPI.writableStream< 'w,>
let close: WebAPI.FileAPI.fileSystemWritableFileStream => Promise.t< unit,>
let getWriter: WebAPI.FileAPI.fileSystemWritableFileStream => WebAPI.FileAPI.writableStreamDefaultWriter< 'w,>
let seek: ( WebAPI.FileAPI.fileSystemWritableFileStream, int,) => Promise.t<unit>
let truncate: ( WebAPI.FileAPI.fileSystemWritableFileStream, int,) => Promise.t<unit>
let write: ( WebAPI.FileAPI.fileSystemWritableFileStream, DataView.t,) => Promise.t<unit>
let write2: ( WebAPI.FileAPI.fileSystemWritableFileStream, ArrayBuffer.t,) => Promise.t<unit>
let write3: ( WebAPI.FileAPI.fileSystemWritableFileStream, WebAPI.FileAPI.blob,) => Promise.t<unit>
let write4: ( WebAPI.FileAPI.fileSystemWritableFileStream, string,) => Promise.t<unit>
let write5: ( WebAPI.FileAPI.fileSystemWritableFileStream, WebAPI.FileAPI.writeParams,) => Promise.t<unit>