Update nifti_writer.py (#1299)
Update nifti_writer.py (#1299)

* add argument for output dtype

Signed-off-by: alxaline <b82af3b14c4ae12eb54054ea4c760d481032bdd0@gmail.com>

* add argument for output dtype for all return

Signed-off-by: alxaline <b82af3b14c4ae12eb54054ea4c760d481032bdd0@gmail.com>

* add output_type in docstring

Signed-off-by: alxaline <b82af3b14c4ae12eb54054ea4c760d481032bdd0@gmail.com>
Project-MONAI/MONAI,Project-MONAI/MONAI,Project-MONAI/MONAI,Project-MONAI/MONAI