code: def to_file_map(self, file_map=None):
      file_map = self.file_map if file_map is None else file_map
      with file_map["image"].get_prepare_fileobj("wb") as fobj:
          np.save(fobj, self.dataobj)
  
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 2 for calling the DoNumpyImage obj's underlying member method code with example usage: obj.to_file_map(file_map) without return types