EDIT

package eu.etaxonomy.taxeditor.editor.descriptiveDataSet.matrix.categorical;

import java.util.Collection;

import org.eclipse.nebula.widgets.nattable.data.convert.DisplayConverter;

            // the values in the Collection

            // So by removing the leading and ending

            // character, we remove the brackets

            String result = canonicalValue.toString();

            result = result.substring(1, result.length() - 1);

            return result;