`shiny.ui.accordion_panel` stopped working with HTML type input parameter due to changes in htmltools dependency

[vinaybenny]

shiny.ui.accordion_panel checks if the title parameter is an instance of str. It used to work with express.ui.HTML type input parameters, like ui.markdown. express.ui.HTML inherits from htmltools dependency. htmltools has undergone a change from version 0.6.0 wherein the HTML type no longer inherits from str. This breaks the isinstance(title, str) check that happens in the shiny.ui.accordion_panel.

With htmltools v0.5.3:

With htmltools v0.6.0:

[gadenbuie]

Here's a small example.

from shiny import ui

ui.accordion_panel(
    ui.HTML("<em>Panel 1</em>"),
    ui.p("This is the content of Panel 1"),
)

Which returns this error message

Traceback (most recent call last):
  File "/Users/garrick/..snip../issue-1827.py", line 3, in <module>
    ui.accordion_panel(
  File "/Users/garrick/..snip../shiny/ui/_accordion.py", line 346, in accordion_panel
    raise ValueError("If `title` is not a string, `value` must be provided")
ValueError: If `title` is not a string, `value` must be provided

What this indicates is that, if title is not a string, then you need to provide the value argument, which uniquely identifies that accordion panel. So this will work:

from shiny import ui

ui.accordion_panel(
    ui.HTML("<em>Panel 1</em>"),
    ui.p("This is the content of Panel 1"),
    value="panel-1"
)