ModemManager will load:
1) The list of supported bands. Note that this doesn't mean that any possible
combination of bands is supported, as modems may support only specific
combinations, but at least gives a rough idea of what the modem is capable
of handling.
2) The list of CURRENT bands. There is no such "Allowed" bands, as we do with
modes, modems will have a specific set of bands being currently used, which
will be reported in the `Bands' property.
If the modem allows modifying the list of bands to use, this can be done with
the `SetBands()' method. If the modem doesn't support using a specific
combination of bands, this method will report an error.
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