How to set `ds` and `cs` for complicated/unsual customized surroundings?

[hrcHarry]

Hi

I have the following customized surrounding:

let g:surround_{char2nr("`")} = "``\r''"

So if we have the text text, it can be surrounded as ``text''.

But, now, I have no idea how to set ds to remove the surrounding ``'' even though I've tried

nmap ds` <Plug>Dsurround`

or

nmap ds` <Plug>Dsurround``''

or something else. (ref: #329)

Furthermore, say, I have another customized surrounding as follows:

let g:surround_{char2nr("m")} = "\\(\r\\)"

Then the map

cs`m

fails to change ``text'' to \(text\).

I have also checked the doc for customizing and #358, but there is no remedy for this. Other posts like #117, #376, #355, and #358 are also checked.