code: def datapt_to_system(self, datapt, system=None, coords='data',
                           naxispath=None):
          
          if self.coordsys == 'raw':
              raise WCSError("No usable WCS")
  
          raise NotImplementedError
docs: Map points to given coordinate system.
  
          Parameters
          ----------
          datapt : array-like
              Pixel coordinates in the format of
              ``[[x0, y0, ...], [x1, y1, ...], ..., [xn, yn, ...]]``.
  
          system : str or None, optional, default to 'icrs'
              Coordinate system name.
  
          coords : 'data' or None, optional, default to 'data'
              Expresses whether the data coordinate is indexed from zero
  
          naxispath : list-like or None, optional, defaults to None
              A sequence defining the pixel indexes > 2D, if any
  
          Returns
          -------
          wcspt : array-like
              WCS coordinates in the format of
              ``[[ra0, dec0], [ra1, dec1], ..., [ran, decn]]``.