private JPanel createDefaultValuePanel() {
            final JPanel defaultValuePanel = new JPanel(new VerticalFlowLayout(VerticalFlowLayout.TOP, 4, 2, true, false));
            final Document doc = PsiDocumentManager.getInstance(getProject()).getDocument(item.defaultValueCodeFragment);
            myDefaultValueEditor = new EditorTextField(doc, getProject(), getFileType());
            final JBLabel defaultValueLabel =
              new JBLabel(RefactoringBundle.message("changeSignature.default.value.label"), UIUtil.ComponentStyle.SMALL);
            defaultValuePanel.add(defaultValueLabel);
            defaultValuePanel.add(myDefaultValueEditor);
            myDefaultValueEditor.setPreferredWidth(getTable().getWidth() / 2);
            myDefaultValueEditor.setFont(EditorUtil.getEditorFont());
            // The corresponding PyParameterInfo field can't be updated by just RowEditorChangeListener(1) 
            // because the corresponding column value is not String but Pair<PsiCodeFragment, Boolean>.
            myDefaultValueEditor.addDocumentListener(new DocumentListener() {
              @Override
              public void documentChanged(@NotNull DocumentEvent event) {
                item.parameter.setDefaultValue(myDefaultValueEditor.getText().trim());
              }
            });
            myDefaultValueEditor.addDocumentListener(mySignatureUpdater);
            return defaultValuePanel;
          }
private JPanel createDefaultValuePanel()