The pre-processing step, run as part of upstartr::run_process
during the process.R stage of a startr project, logs all variables
currently in the global environment, which will then be removed during the
post-processing step to keep the startr environment unpolluted.
begin_processing(should_clean_processing_variables = TRUE)Either TRUE, FALSE, or pulled from the environment if set.
A list of all environment variables present before the function was run