g
``decrypt`` or ``encrypt``.

By *associated data* it is meant any data (e.g. packet headers) that
will not be encrypted and will be transmitted in the clear.
However, the receiver is still able to detect any modification to it.
In CCM, the *associated data* is also called
*additional authenticated data* (AAD).

If there is no associated data, this method must not be called.

The caller may split associated data in segments of any size, and
invoke this method multiple times, each time with the next segment.

:Parameters:
  assoc_data : bytes/bytearray/memoryview
    A piece of associated data. There are no restrictions on its size.
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