Check if there is already a field_name field in the current class
           It is useful before allowing to rename a field to check name does
           not already exist.

def field_name_exist(self, field_name):
        """Check if there is already a field_name field in the current class
           It is useful before allowing to rename a field to check name does
           not already exist.
        """

        fields = self.class_item.get_fields()
        for f in fields:
            if f.name == field_name:
                return True
        return False