code: def get_data(self, data_x, data_y):
          
          image = self.get_image()
          if image is not None:
              return image.get_data_xy(data_x, data_y)
  
          raise ImageViewNoDataError("No image found")
docs: Get the data value at the given position.
          Indices are zero-based, as in Numpy.
  
          Parameters
          ----------
          data_x, data_y : int
              Data indices for X and Y, respectively.
  
          Returns
          -------
          value
              Data slice.
  
          Raises
          ------
          ginga.ImageView.ImageViewNoDataError
              Image not found.