docs: def asarray(self, *args, **kwargs):
          """Read image data from file and return as numpy array."""
          # TODO: fix TypeError on Python 2
          #   "TypeError: unbound method asarray() must be called with TiffPage
          #   instance as first argument (got TiffFrame instance instead)"
          if self._keyframe is None:
              raise RuntimeError('keyframe not set')
          kwargs['validate'] = False
          return TiffPage.asarray(self, *args, **kwargs)