# File lib/dbi.rb, line 171
        def trace(mode=nil, output=nil)
            # FIXME trace
            raise InterfaceError, "the trace module has been removed until it actually works."
            @@trace_mode   = mode   || @@trace_mode   || DBI::DEFAULT_TRACE_MODE
            @@trace_output = output || @@trace_output || DBI::DEFAULT_TRACE_OUTPUT
        end