code: def set_data_dtype(self, dtype):
      self._dataobj = self._dataobj.astype(dtype)
  
file_path: nibabel/nibabel/tests/test_dataobj_images.py
imports: import numpy
  from nibabel.dataobj_images import DataobjImage
  from nibabel.filebasedimages import FileBasedHeader
  from nibabel.tests.test_filebasedimages import TestFBImageAPI
  from nibabel.tests.test_image_api import DataInterfaceMixin
label_desc: Use image node_id 4 for calling the DoNumpyImage obj's underlying member method code with example usage: obj.set_data_dtype(dtype) without return types