64-bit integer AVPs will be serialized as a 4-byte Integer

[ofraiwan]

This case occurs when the AVP value should be a 64-bit integer per the Diameter standards.
So, constructing an AVP using the DiameterAVP class will serialize the data as a 32-bit integer.

avp = DiameterAVP(code=439, data=1)

Checking the avp.data attribute, you will see only 4 bytes where they should be 8 bytes.

Ref: https://github.com/heimiricmr/bromelia/blob/master/docs/avps.md#constructor