`list_flatten()` works recursively through an input list and puts all
elements of nested list to the top level. If there are no nested lists
then the input is returned unchanged.
Usage
list_flatten(in_list, max_depth = -1)
Value
A list without nested lists.
Arguments
in_list
The list to flatten
max_depth
Maximum depth to recurse into.
Details
Using `max_depth` you can control whether to flatten all nested lists.
Negative values will cause all nested lists to be flattened, positive
depths will limit the depth of the recursion.