Allow +2 more missing N-term residues

[prihoda]

Currently Elipovimab sequence is not supported because it misses 8 n-term residues in L chain:

HC: QMQLQESGPGLVKPSETLSLTCSVSGASISDSYWSWIRRSPGKGLEWIGYVHKSGDTNYNPSLKSRVHLSLDTSKNQVSLSLTGVTAADSGKYYCARTLHGRRIYGIVAFNEWFTYFYMDVWGTGTQVTVSS

LC: SDISVAPGETARISCGEKSLGSRAVQWYQHRAGQAPSLIIYNNQDRPSGIPERFSGSPDSRPGTTATLTITSVEAGDEADYYCHIWDSRVPTKWVFGGGTTLTVL

Numbered:

       L9 S
      L10 D
      L11 I
      L12 S
      L13 V
      ...

Would it be safe to allow 8 missing N-term residues - starting from at least IMGT L9?

Example:

from ImmuneBuilder import ABodyBuilder2

ABodyBuilder2().predict({
  'H': 'QMQLQESGPGLVKPSETLSLTCSVSGASISDSYWSWIRRSPGKGLEWIGYVHKSGDTNYNPSLKSRVHLSLDTSKNQVSLSLTGVTAADSGKYYCARTLHGRRIYGIVAFNEWFTYFYMDVWGTGTQVTVSS', 
  'L': 'SDISVAPGETARISCGEKSLGSRAVQWYQHRAGQAPSLIIYNNQDRPSGIPERFSGSPDSRPGTTATLTITSVEAGDEADYYCHIWDSRVPTKWVFGGGTTLTVL'
}).save('Elipovimab_predicted.pdb')

Superimposition of predicted structure (pink) with 4fq1 ground truth (green):

Elipovimab_prediction.cif.zip