def reverse_field_not_already_registered(model_field: "ForeignKeyField") -> bool:
    """
    Checks if child is already registered in parents pydantic fields.

    :raises ModelDefinitionError: if related name is already used but lead to different
    related model
    :param model_field: original relation ForeignKey field
    :type model_field: relation Field
    :return: result of the check
    :rtype: bool
    """
    related_name = model_field.get_related_name()
    check_result = related_name not in model_field.to.ormar_config.model_fields
    check_result2 = (
        model_field.owner.get_name() not in model_field.to.ormar_config.model_fields
    )

    if not check_result:
        verify_related_name_dont_duplicate(
            related_name=related_name, model_field=model_field
        )
    if not check_result2:
        verify_related_name_dont_duplicate(
            related_name=model_field.owner.get_name(), model_field=model_field
        )

    return check_result and check_result2

    Checks if child is already registered in parents pydantic fields.

    :raises ModelDefinitionError: if related name is already used but lead to different
    related model
    :param model_field: original relation ForeignKey field
    :type model_field: relation Field
    :return: result of the check
    :rtype: bool
    
ormar/models/helpers/relations.py