flatten org-cite-supported-styles

styles.el

;; https://github.com/jkitchin/org-ref/issues/885#issuecomment-885682807
;; doesn't currently handle the nil style correctly
(defun oc-bibtex-actions--simple-styles (&optional targets)
  (let ((styles (org-cite-supported-styles targets)))
    (cl-loop for group in styles append
	     (let ((main (pop group)))
	       (when (string= "nil" (car main)) (setf (car main) ""))
	       (append (list (car main))
		       (cl-loop for rest in group collect
				;; needs to remove "/nil"
			        (format "%s/%s"
				        (car main)
				        (car (cdr rest)))))))))