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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _get_proj4_name(self, projection):
 """Map CF projection name to PROJ.4 name."""

        gmap_name = projection.attrs['grid_mapping_name']
        proj = {
            'geostationary': 'geos',
            'lambert_conformal_conic': 'lcc',
            'polar_stereographic': 'stere',
            'mercator': 'merc',
        }.get(gmap_name, gmap_name)
        return proj