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# Source code for astropy.coordinates.builtin_frames.icrs

    # -*- coding: utf-8 -*-
    # Licensed under a 3-clause BSD style license - see LICENSE.rst
    from __future__ import (absolute_import, unicode_literals, division,
                            print_function)

    from ..representation import SphericalRepresentation
    from ..baseframe import BaseCoordinateFrame, RepresentationMapping

    class ICRS(BaseCoordinateFrame):
        """
        A coordinate or frame in the ICRS system.

        If you're looking for "J2000" coordinates, and aren't sure if you want to
        use this or `~astropy.coordinates.FK5`, you probably want to use ICRS. It's
        more well-defined as a catalog coordinate and is an inertial system, and is
        very close (within tens of milliarcseconds) to J2000 equatorial.

        For more background on the ICRS and related coordinate transformations, see the
        references provided in the  :ref:`astropy-coordinates-seealso` section of the
        documentation.

        Parameters
        ----------
        representation : `BaseRepresentation` or None
            A representation object or None to have no data (or use the other keywords)
        ra : `Angle`, optional, must be keyword
            The RA for this object (``dec`` must also be given and ``representation``
            must be None).
        dec : `Angle`, optional, must be keyword
            The Declination for this object (``ra`` must also be given and
            ``representation`` must be None).
        distance : `~astropy.units.Quantity`, optional, must be keyword
            The Distance for this object along the line-of-sight.
            (``representation`` must be None).
        """

        frame_specific_representation_info = {
            'spherical': [RepresentationMapping('lon', 'ra'),
                          RepresentationMapping('lat', 'dec')]
        }
        frame_specific_representation_info['unitspherical'] = \
            frame_specific_representation_info['spherical']

        default_representation = SphericalRepresentation