@Nullable
  private static PyExpression getReferenceQualifier(@NotNull PsiReference reference) {
    final PsiElement element = reference.getElement();

    if (element instanceof PyQualifiedExpression) {
      final PyExpression qualifier = ((PyQualifiedExpression)element).getQualifier();
      if (qualifier != null) {
        return qualifier;
      }
    }

    if (reference instanceof PyFromImportNameReference) {
      final PyFromImportStatement statement = PsiTreeUtil.getParentOfType(element, PyFromImportStatement.class);
      if (statement != null) {
        final PyReferenceExpression source = statement.getImportSource();
        if (source != null) {
          return source;
        }
      }
    }

    return null;
  }
@Nullable
  private static PyExpression getReferenceQualifier(@NotNull PsiReference reference)