convert ee.ImageCollection to numpy.ndarray type

[eeedasc]

Hi Prof. Qiusheng,
I get the Landsat 8 image with ee.ImageCollection and I want to use the 'rasterio' module. But I guess, I have requirement the 'numpy.ndarray' for use with rasterio.
Can you help me, please?
Thank you.
Code is;

image4 = (
ee.ImageCollection("LANDSAT/LC08/C01/T1")
.filterBounds(region)
.filterDate('2020-08-01', '2020-08-30')
.filterMetadata('CLOUD_COVER', 'less_than', 0.5)
.mosaic()
.clip(region)
.select('B4')
)

with rasterio.open(url+nirband) as src: ---> I must change to float with this code.
nirImage = src.read(1).astype('f4')