highlight() function: setting the 'off' event to 'plotly_unhover' results in an error.

This is a modified example from here:

library(plotly)

# load the `txhousing` dataset
data(txhousing, package = "ggplot2")

# declare `city` as the SQL 'query by' column
tx <- highlight_key(txhousing, ~city)

# initiate a plotly object
base <- plot_ly(tx, color = I("black")) %>% 
  group_by(city)

# create a time series of median house price
time_series <- base %>%
  group_by(city) %>%
  add_lines(x = ~date, y = ~median)

highlight(
  time_series, 
  on = "plotly_hover",
  off = "plotly_hover", # causes error
  selectize = FALSE, 
  dynamic = FALSE,
  color = "red",
  persistent = FALSE
)

Not providing off results in a warning:

Setting the off event (i.e., 'plotly_doubleclick') to match the on event (i.e., 'plotly_hover'). You can change this default via the highlight() function.

Setting off to plotly_hover or plotly_unhover (my initial intention) results in an error:

Error in match.arg(off, off_options) :
'arg' should be one of “plotly_doubleclick”, “plotly_deselect”, “plotly_relayout”

Found this via: https://stackoverflow.com/a/64387370/9841389

PS: using the latest CRAN version of plotly.

Start at the highlight() entry point and reproduce the modified txhousing example with off set to plotly_hover and plotly_unhover. Inspect the off_options validation and compare it with the documented event behavior; done means valid off events no longer raise the reported match.arg error and the example behaves as intended.