sub accessor_to_column {
  my ($proto,$column) = @_;
  my $class = ref $proto || $proto;

  # note the lexical variable to store class data
  my $found_column = 'id' eq $column
    ? $CLASS_DATA{$class}{id}
    : $CLASS_DATA{$class}{accessor_to_column}{$column};

  unless ($found_column) {
    croak "No column found for ($column)";
  }
  return $found_column;
}