the question of converting protein sequences to corresponding codes

[laplacezj]

On the matter of converting protein sequences into corresponding codes, I noticed that you utilized a dictionary called self. letter_to_num to facilitate this conversion process within your dataset. In regards to this particular dictionary, I would like to inquire about its design concept and the rationale behind utilizing such an encoding format. Additionally, if my protein sequence contains an unknown residue represented by X, how should it be encoded?