trace (SQLite3::Driver::Native::Driver)

    # File lib/sqlite3/driver/native/driver.rb, line 52
        def trace( db, data=nil, &block )
          if block
            cb = API::CallbackData.new
            cb.proc = block
            cb.data = data
            result = API.sqlite3_trace( db, API::Sqlite3_ruby_trace, cb )
            @trace[db] = cb # see comments in busy_handler
          else
            result = API.sqlite3_trace( db, nil, nil )
            @trace.delete(db) # see comments in busy_handler
          end

          result
        end