Set option value by subset operator

# S3 method for GlobalOptionsFun
[[(x, nm) <- value

Arguments

x	the option object returned by `set_opt` or `setGlobalOptions`.
nm	a single option name.
value	the value which is assigned to the option.

opt[["a"]] = 1 is same as opt("a" = 1) or opt$a = 1.

Zuguang Gu <z.gu@dkfz.de>

opt = set_opt(a = 1)
opt[["a"]] = 2
opt$a
#> [1] 2