v0.7.2: Allow for the absence of pairing.a3m in inference.

What's changed

• If the directory specified by precomputed_msa_dir under the msa field in the inference file does not contain the pairing.a3m file, no error will be thrown; instead, only the non_pairing.a3m file will be used for inference. In previous versions, this would have caused an immediate error.

example.json

[{
    "sequences": [
        {
            "proteinChain": {
                "sequence": "MGSSHHHHHHSSGLVPRGSHMSGKIQHKAVVPAPSRIPLTLSEIEDLRRKGFNQTEIAELYGVTRQAVSWHKKTYGGRLTTRQIVQQNWPWDTRKPHDKSKAFQRLRDHGEYMRVGSFRTMSEDKKKRLLSWWKMLRDNDLVLEFDPSIEPYEGMAGGGFRYVPRDISDDDLLIRVNEHTQLTAEGELLWSWPDDIEELLSEP",
                "count": 1,
                "msa": {
                    "precomputed_msa_dir": "./examples/7r6r/msa/1",
                    "pairing_db": "uniref100"
                }
            }
        },
        {
            "dnaSequence": {
                "sequence": "TTTCGGTGGCTGTCAAGCGGG",
                "count": 1
            }
        },
        {
            "dnaSequence": {
                "sequence": "CCCGCTTGACAGCCACCGAAA",
                "count": 1
            }
        }
    ],
    "name": "7r6r"
}
]