AF3 unable to predict covalent bonds between DNA and protein

Hi there!

I read the input doc and it says **Defining covalent bonds between or within polymer entities is not currently supported**.

I'm not sure what `polymer` exactly means in the context.So I use 1K4T, a protein-DNA covalent complex and `run_alphafold.py` gives an info:

```log
I1201 13:58:33.149596 128177626838144 structure_cleaning.py:253] Reducing number of bonds for top1_dna_topotecan_hg from 1 to 0, of which 1 are polymer-polymer bonds and 0 are bad bonds.
```

And finally in pymol that bond doesn't show up.

So,does `polymer` in `#Bond` section mean proteins,DNA, and RNA exactly?

Does it mean that covalent bond definition for protein/DNA/RNA is not supported now,while ligand-ligand,ligand-protein,ligand-DNA and ligand-RNA are supported?

If I DO want to model a protein-DNA covalent complex,is it reasonable to define a single DT as a ligand and connect to the protein and other DNA units?