Default callback function for processing API response content. This function converts data frames within lists to data.table objects for better performance and functionality, if the data.table package is available.
Details
The function recursively processes list responses and converts any data.frame
objects to data.table objects using data.table::as.data.table(), but only
if the data.table package is installed. If data.table is not available,
data frames are returned unchanged. Non-data.frame elements are always
returned unchanged.