the table that the practice definitions can be found
out_dir
a directory to output to. This will be created if it does not already exist
file_type
the type of file to be saved. This can be one of "txt", "csv", "rda", "dta".
...
arguments to be passed to export_fn
Defaults to exporting consultation tables for use by match_on_index(). the full path
to out_dir will be created if it does not already exist.