def shell_select(self, ra, dec, r_in, r_out, center_ra, center_dec):
        """

        :param ra:
        :param dec:
        :param r_in:
        :param r_out:
        :param center_ra:
        :param center_dec:
        :return:
        """
        x = ra - center_ra
        y = dec - center_dec
        R = np.sqrt(x**2 + y**2)
        if (R >= r_in) and (R < r_out):
            return True
        else:
            return False
def shell_select ( self , ra , dec , r_in , r_out , center_ra , center_dec ) : x = ra - center_ra y = dec - center_dec R = np . sqrt ( x ** 2 + y ** 2 ) if ( R >= r_in ) and ( R < r_out ) : return True else : return False
:param ra:
        :param dec:
        :param r_in:
        :param r_out:
        :param center_ra:
        :param center_dec:
        :return: