'AllTables' method in DBIx:.Database returns nothing with CSV files

I am using DBIx::Recordset to access a directory with CSV files, and
the method DBIx::Database->AllTables seems to return just an empty
hash reference. I'm talking about the following code:

  use DBIx::Recordset;
  use Data::Dumper;

  my $db = DBIx::Database -> new ({'!DataSource'   =>
"DBI:CSV:f_dir=db",
                                   '!Username'     =>  "",
                                   '!Password'     =>  "",
                                   '!KeepOpen'     => 1}) ;

  print Dumper $db->AllTables();

The directory 'db' contains the CSV files. Is this a bug in
DBIx::Database that should be reported, or am I missing something?