imMediaExtra
IM extra_data 与内联附件中媒体元数据的读取（缩略图、尺寸、文件大小等）。
主要函数
typescript
function readMediaThumbnailUrlFromExtra(extra?: Record<string, unknown>): string | undefined
function readMediaFileSizeBytesFromExtra(extra?: Record<string, unknown>): number | undefined
function readMediaDimensionsFromExtra(extra?: Record<string, unknown>): { w?: number; h?: number }
function readAttachmentSizeBytesFromRecord(rec: Record<string, unknown>): number | undefined
function readNonNegativeIntField(v: unknown): number | undefined
function readNonNegativeIntFieldOrZero(v: unknown): number