'Return a transform from the specified frame to display coordinates.
This does not include the transData transformation
Parameters
frame : :class:`~astropy.wcs.WCS` or :class:`~matplotlib.transforms.Transform` or str
The ``frame`` parameter can have several possible types:
* :class:`~astropy.wcs.WCS` instance: assumed to be a
transformation from pixel to world coordinates, where the
world coordinates are the same as those in the WCS
transformation used for this ``WCSAxes`` instance. This is
used for example to show contours, since this involves
plotting an array in pixel coordinates that are not the
final data coordinate and have to be transformed to the
common world coordinate system first.
* :class:`~matplotlib.transforms.Transform` instance: it is
assumed to be a transform to the world coordinates that are
part of the WCS used to instantiate this ``WCSAxes``
instance.
* ``\'pixel\'`` or ``\'world\'``: return a transformation that
allows users to plot in pixel/data coordinates (essentially
an identity transform) and ``world`` (the default
world-to-pixel transformation used to instantiate the
``WCSAxes`` instance).
* ``\'fk5\'`` or ``\'galactic\'``: return a transformation from
the specified frame to the pixel/data coordinates.
* :class:`~astropy.coordinates.BaseCoordinateFrame` instance.'

def get_transform(self, frame):

    return (self._get_transform_no_transdata(frame).inverted() + self.transData)
