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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 sky2ang(sky):
 """ Convert ra,dec coordinates to theta,phi coordinates ra -> phi dec -> theta Parameters sky : numpy.array Array of (ra,dec) coordinates. See :func:`AegeanTools.regions.Region.radec2sky` Returns ------- theta_phi : numpy.array Array of (theta,phi) coordinates. """

        try:
            theta_phi = sky.copy()
        except AttributeError as _:
            theta_phi = np.array(sky)
        theta_phi[:, [1, 0]] = theta_phi[:, [0, 1]]
        theta_phi[:, 0] = np.pi/2 - theta_phi[:, 0]
        # # force 0<=theta<=2pi
        # theta_phi[:, 0] -= 2*np.pi*(theta_phi[:, 0]//(2*np.pi))
        # # and now -pi<=theta<=pi
        # theta_phi[:, 0] -= (theta_phi[:, 0] > np.pi)*2*np.pi
        return theta_phi