def get_field_errors(node):
        """ return a list of FieldErrors if the specified securityData element has field errors """
        assert node.name() == 'securityData' and not node.isArray()
        nodearr = node.getElement('fieldExceptions')
        if nodearr.numValues() > 0:
            secid = XmlHelper.get_child_value(node, 'security')
            errors = XmlHelper.as_field_error(nodearr, secid)
            return errors
        else:
            return None
return a list of FieldErrors if the specified securityData element has field errors