def validate_field_name(field_name: str) -> None:
    """Validate the field name.

    We reuse the validation function from structured index, but add some extra validations for unstructured index."""
    try:
        common_validate_field_name(field_name)
    except ValueError as e:
        raise errors.InvalidFieldNameError(str(e))
    # Some extra validations for unstructured index
    if _RESERVED_FIELD_SUBSTRING in field_name:
        raise errors.InvalidFieldNameError(
            f"Field name {field_name} contains the reserved substring {_RESERVED_FIELD_SUBSTRING}. This is a "
            f"reserved substring and cannot be used in field names for unstructured marqo index."
        )
Validate the field name.

    We reuse the validation function from structured index, but add some extra validations for unstructured index.
src/marqo/core/unstructured_vespa_index/unstructured_validation.py