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.arr)
  
imports: import warnings
  from itertools import product
  import numpy
  import pytest
  from ..filebasedimages import FileBasedHeader, FileBasedImage, SerializableImage
  from .test_image_api import GenericImageAPI, SerializeMixin
label_desc: Use image node_id 7 for calling the FBNumpyImage obj's underlying member method code with example usage: obj.to_file_map(file_map) without return types