3.1.0
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* added nfts (beta) endpoints (/nfts/list, /nfts/{id}, /nfts/{asset_platform_id}/contract/{contract_address})
* updated tests
==================
* added nfts (beta) endpoints (/nfts/list, /nfts/{id}, /nfts/{asset_platform_id}/contract/{contract_address})
* updated tests