coc-snippets not expanding/loading custom snippets

Question

I've downloaded a bunch of custom snippets to ~/.custom/snippets/. My snippet files are named python.snippets, cpp.snippets, etc. I don't have ultisnips or any other snippet plugin installed, just coc.nvim and its friends, including coc-snippets.

When I'm working in a python file, :CocCommand snippets.editSnippets opens the correct snippets file. :CocCommand workspace.showOutput snippets returns the following:

[Info REDACTED] Using ultisnips directories: UltiSnips /home/user_name/.custom/snippets
[Info REDACTED] Using ultisnips python command: pyx

Here's the config for coc.nvim in my .vimrc (mostly default settings provided on github):

" coc.nvim
" Use tab for trigger completion with characters ahead and navigate.
" NOTE: Use command ':verbose imap <tab>' to make sure tab is not mapped by
" other plugin before putting this into your config.
inoremap <silent><expr> <TAB>
        \ pumvisible() ? "\<C-n>" :
        \ <SID>check_back_space() ? "\<TAB>" :
        \ coc#refresh()
inoremap <expr><S-TAB> pumvisible() ? "\<C-p>" : "\<C-h>"

function! s:check_back_space() abort
      let col = col('.') - 1
         return !col || getline('.')[col - 1]  =~# '\s'
endfunction

" Use <c-space> to trigger completion.
inoremap <silent><expr> <c-space> coc#refresh()

" Use <cr> to confirm completion, `<C-g>u` means break undo chain at current
" position. Coc only does snippet and additional edit on confirm.
if exists('*complete_info')
    inoremap <expr> <cr> complete_info()["selected"] != "-1" ? "\<C-y>" : "\<C-g>u\<CR>"
else
        imap <expr> <cr> pumvisible() ? "\<C-y>" : "\<C-g>u\<CR>"
endif

" Use `[g` and `]g` to navigate diagnostics
nmap <silent> [g <Plug>(coc-diagnostic-prev)
nmap <silent> ]g <Plug>(coc-diagnostic-next)

" GoTo code navigation.
nmap <silent> gd <Plug>(coc-definition)
nmap <silent> gy <Plug>(coc-type-definition)
nmap <silent> gi <Plug>(coc-implementation)
nmap <silent> gr <Plug>(coc-references)

" Use K to show documentation in preview window.
nnoremap <silent> K :call <SID>show_documentation()<CR>

function! s:show_documentation()
if (index(['vim','help'], &filetype) >= 0)
        execute 'h '.expand('<cword>')
else
        call CocAction('doHover')
    endif
endfunction

" Highlight the symbol and its references when holding the cursor.
autocmd CursorHold * silent call CocActionAsync('highlight')

" Symbol renaming.
nmap <leader>rn <Plug>(coc-rename)

" Formatting selected code.
xmap <leader>f  <Plug>(coc-format-selected)
nmap <leader>f  <Plug>(coc-format-selected)

augroup mygroup
autocmd!
" Setup formatexpr specified filetype(s).
autocmd FileType typescript,json setl formatexpr=CocAction('formatSelected')
" Update signature help on jump placeholder.
    autocmd User CocJumpPlaceholder call CocActionAsync('showSignatureHelp')
augroup end

" Applying codeAction to the selected region.
" Example: `<leader>aap` for current paragraph
xmap <leader>a  <Plug>(coc-codeaction-selected)
nmap <leader>a  <Plug>(coc-codeaction-selected)

" Remap keys for applying codeAction to the current line.
nmap <leader>ac  <Plug>(coc-codeaction)
" Apply AutoFix to problem on the current line.
nmap <leader>qf  <Plug>(coc-fix-current)

" Introduce function text object
" NOTE: Requires 'textDocument.documentSymbol' support from the language server.
xmap if <Plug>(coc-funcobj-i)
xmap af <Plug>(coc-funcobj-a)
omap if <Plug>(coc-funcobj-i)
omap af <Plug>(coc-funcobj-a)

" Use <TAB> for selections ranges.
" NOTE: Requires 'textDocument/selectionRange' support from the language server.
" coc-tsserver, coc-python are the examples of servers that support it.
nmap <silent> <TAB> <Plug>(coc-range-select)
xmap <silent> <TAB> <Plug>(coc-range-select)

" Add `:Format` command to format current buffer.
command! -nargs=0 Format :call CocAction('format')

" Add `:Fold` command to fold current buffer.
command! -nargs=? Fold :call     CocAction('fold', <f-args>)

" Add `:OR` command for organize imports of the current buffer.
command! -nargs=0 OR   :call     CocAction('runCommand', 'editor.action.organizeImport')

" Add (Neo)Vim's native statusline support.
" NOTE: Please see `:h coc-status` for integrations with external plugins that
" provide custom statusline: lightline.vim, vim-airline.
set statusline^=%{coc#status()}%{get(b:,'coc_current_function','')}

" Mappings using CoCList:
" Show all diagnostics.
nnoremap <silent> <space>a  :<C-u>CocList diagnostics<cr>
" Manage extensions.
nnoremap <silent> <space>e  :<C-u>CocList extensions<cr>
" Show commands.
nnoremap <silent> <space>c  :<C-u>CocList commands<cr>
" Find symbol of current document.
nnoremap <silent> <space>o  :<C-u>CocList outline<cr>
" Search workspace symbols.
nnoremap <silent> <space>s  :<C-u>CocList -I symbols<cr>
" Do default action for next item.
nnoremap <silent> <space>j  :<C-u>CocNext<CR>
" Do default action for previous item.
nnoremap <silent> <space>k  :<C-u>CocPrev<CR>
" Resume latest coc list.
nnoremap <silent> <space>p  :<C-u>CocListResume<CR>

" coc-snippets
let g:coc_snippet_next = '<c-j>'
let g:coc_snippet_prev = '<c-k>'
imap <C-Space> <Plug>(coc-snippets-expand)
imap <C-j> <Plug>(coc-snippets-expand-jump)

This is my ~/.vim/coc-settings.json file:

// .vim/coc-settings.json
{
    "suggest.autoTrigger": "trigger",
    "suggest.triggerAfterInsertEnter": true,
    "snippets.userSnippetsDirectory": "$HOME/.custom/snippets"
}

Pressing <C-Space> should give me snippets. However, it doesn't seem to be giving me the right snippets from ~/.custom/snippets/. I'm not sure if it's loading the snippets correctly and I've done some basic checking from the repo's FAQ.

How should I configure my coc-snippets?