Some keywords can't be completed in the *dap-ui-repl* buffer, which is a comint derivative mode.

[Hongyi Zhao]

On Ubuntu 20.04.3 LTS, I'm using the self-compiled git master version
of Emacs, and installed the dap-mode through straight with the
following configuration:


```emacs-lisp
(use-package dap-mode
  :after lsp-mode
  :config
  ;;https://github.com/emacs-lsp/dap-mode/issues/372#issuecomment-720716281
  (setq dap-auto-configure-features '(sessions locals breakpoints
expressions repl controls tooltip)
    ;;https://emacs-lsp.github.io/dap-mode/page/configuration/#python
    ;;$ pyenv shell datasci
    ;;$ pip install debugpy
    
;;https://github.com/emacs-lsp/dap-mode/blob/00e1a5d70c32019800b8eb09d2fbcecbcb727a16/dap-python.el#L163
    ;; C-h o RET dap-python-debugger RET
        dap-python-debugger 'debugpy)

  ;;This will add the python related configuration to dap-debug.
  (require 'dap-python)

  ;; Bind `C-c l d` to `dap-hydra` for easy access
  ;;(general-define-key
  ;;  :keymaps 'lsp-mode-map
  ;;  :prefix lsp-keymap-prefix
  ;;  "d" '(dap-hydra t :wk "debugger"))
  )
```

But I find that some keywords can't be completed in the *dap-ui-repl*
buffer, for example, import, as shown in the attachment.

Any hints for solving this problem? See here [1] for relevant discussion.

[1] https://github.com/emacs-lsp/dap-mode/issues/544

Regards,
HZ