Exporting image and NoData pixels were filled with values, is there a way to keep the original image exported?

[Lut-hfi]

I am new to geemap. I displayed image in GEE code editor and found there are NoData pixels inside my AOI (an island). Then I use geemap in python to export the image to local drive. Here is the code looks like

geemap.ee_export_image(lst_img, filename="viirs_lst.tif", scale=1000, region=aoi)

lst_image is the image, aoi is a polygon (bounding box defined by coordinates). When I displayed the exported image in QGIS I found that the NoData pixels inside the island were filled with values, not becoming NoData pixels anymore. Is it a normal process performed by geemap? Is there any option to keep the original image exported?

Thank you,
Luthfi

[Lut-hfi]

I found the problem. I made mistake in bitwise operation when filtering the image using QC bands. Thank you for all your attention.