NIMQChatAttachmentDownloadParam 成员列表

成员的完整列表，这些成员属于 NIMQChatAttachmentDownloadParam,包括所有继承而来的类成员

cb	NIMQChatAttachmentDownloadParam
file_path	NIMQChatAttachmentDownloadParam
progress_cb	NIMQChatAttachmentDownloadParam
res_type	NIMQChatAttachmentDownloadParam
task_id	NIMQChatAttachmentDownloadParam
url	NIMQChatAttachmentDownloadParam
user_data	NIMQChatAttachmentDownloadParam