[spam] [personal] perceiver model notes

[k]

## num_self_attends_per_block ##

- number of self attention layers

configuration object is
transformers.models.perceiver.configuration_perceiver.PerceiverConfig
and it briefly documents the parameters (and likely a few more).

configs deriving from perceiverconfig can simply set attribute to add
more configs

the perceiver classes are aliased into transformers at the top level

import transformers
config = transformers.PerceiverConfig()
model = transformers.PerceiverModel(config)