to_count_filter() and to_mention_filter() converts a query() to a vector
of filters appropriate for either counting or fetching mentions. An account code
is specified to choose a filter for a specific account.
Each filter is required to perform all of the count operations or
to fetch all of the queried data.
to_count_filter(query, code)
| query | A   | 
    
|---|---|
| code | The account we want filters for.  | 
    
A vector of characters. Returns NULL if there are no brands.
Other query conversion functions: 
to_mention_filter()
#> (published inthelast week) and (brand isorchildof 1 or brand isorchildof 2)