keys of a container into a list.
transform arguments should be
functions of one argument. If
filter is non-nil, then the
list returned will contain only
keys that return true. If
transform is non-nil, then it will be applied to each key
that passes the filter.
|collect-keys < associative-container-mixin >|
|collect-keys < hash-table >|
|collect-keys < list >|
|collect-keys < stable-associative-container >|