code: def mean(self):
          
          with cython_context():
              if self.dtype == _Image:
                  from  .. import extensions
                  return extensions.generate_mean(self)
              else:
                  return self.__proxy__.mean()
docs: Mean of all the values in the SArray, or mean image.
  
          Returns None on an empty SArray. Raises an exception if called on an
          SArray with non-numeric type or non-Image type.
  
          Returns
          -------
          out : float | turicreate.Image
              Mean of all values in SArray, or image holding per-pixel mean
              across the input SArray.