Return keys from hast tables, plists, and alists

This function returns keys from hast tables, plists, and alists.  
Should I include anything less or more to it?

(defun aplt-keys (tpal)
  "Return keys from ALIST, PLIST, or HASH-TABLE.
INPUT alist, plist, or hash-table"

  (cond
     ;; HASH TABLE
     ((hash-table-p tpal)
         (hash-table-keys tpal))

     ;; Property List (PLIST)
     ((and (listp tpal) (cl-evenp (length tpal)) (plistp tpal))
         (let (keys)
            (while tpal
               (push (car tpal) keys)
               (setq tpal (cddr tpal)))
               (nreverse keys)))
    
     ;; Association List (ALIST)
     ((and (listp tpal) (alistp tpal))
         (mapcar #'car tpal))

     (t  (message "Input Type not supported: %s" (type-of tpal)))))