The contig input

[markobabic333]

Can someone please help me understand the contig input syntax because its fairly confusing.
On the bottom of the Google Colab notebook there are instructions:

• contigs='A1-10' pdb='6MRR' - keep first 10 positions fixed, noise the rest
  and
• contigs='40/A163-181/40' pdb='5TPN'
  Now, my small peptide doesnt contain chain IDs, so I tried putting in "4-8" and 3/4-8/3. The program responds by writing out the following:
  Processing 3, first part is 3
  Processing 4-8, first part is 4
  Processing 3, first part is 3
  mode: free
  output: outputs/test_ouret
  contigs: ['3-3/8-8/3-3']
  or
  Processing 4-8, first part is 4
  mode: free
  output: outputs/test_uhkxk
  contigs: ['5-5']

What am I doing wrong? Why is the code interpreting me wanting to keep sequence residues 4 through 8 as wanting to either keep 8-8 or 5-5?

This isnt even the final result I want from this. Im just testing out to understand the syntax better.
I uploaded a 11 amino acid peptide and I want it to keep residues 4, 6 and 8 intact, while changing the other residues to keep 4, 6 and 8 in the same geometric positions. And I'm really struggling on how to do that.
Please, any help would be greatly appreciated.

[markobabic333]

I found out the problem myself, but Im gonna leave the solution here so someone can find it.
Chain names need to be generated in the uploaded PDB file for the contig to function.

I guess developers never thought someone was going to generate a sequence using the 'fab' command in PyMol without specifying the chain ID.