@classmethod
def from_instrument(cls, instr_name):
    """
        Obtain an instrumental background spectrum corresponding
        to a registered instrument.

        Parameters
        ----------
        instr_name : string
            Name of the instrument in the instrument registry.
        """
    from soxs.instrument_registry import instrument_registry
    from soxs.background.instrument import instrument_backgrounds
    instr = instrument_registry[instr_name]
    return instrument_backgrounds[instr['bkgnd']]
