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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 _coords2idx(self, coords):
 """ Converts from sky coordinates to pixel indices. Args: coords (:obj:`astropy.coordinates.SkyCoord`):
 Sky coordinates. Returns: Pixel indices of the coordinates, with the same shape as the input coordinates. Pixels which are outside the map are given an index equal to the number of pixels in the map. """


        x = self._coords2vec(coords)
        idx = self._kd.query(x, p=self._metric_p,
                             distance_upper_bound=self._max_pix_scale)
        return idx[1]