You have governance rules, no problem

# src/my_org_validators/steward.py
"""StewardRequired — every contract MUST declare a steward identifier."""

from __future__ import annotations

from typing import Any, List, Mapping

from fluid_sdk import ContractHelper, Finding, PluginMetadata, Validator


class StewardRequired(Validator):
    """Every contract must carry metadata.labels['principal.steward.id']."""

    name = "steward-required"

    @classmethod
    def get_plugin_info(cls) -> PluginMetadata:
        return PluginMetadata(
            name=cls.name,
            role=cls.role,
            display_name="Steward Required Validator",
            description="Every contract must declare a data steward identifier.",
            version="0.1.0",
            author="my-org platform team",
            tags=["governance", "compliance"],
        )

    def plan(self, contract: Mapping[str, Any]) -> List[dict]:
        c = ContractHelper(contract)
        findings: List[Finding] = []

        labels = c.metadata.get("labels") or {}
        steward_id = labels.get("principal.steward.id")
        steward_email = labels.get("principal.steward.email")

        if not steward_id:
            findings.append(Finding(
                severity="error",
                code="STEWARD_ID_MISSING",
                message=(
                    f"Contract {c.id!r} is missing the required label "
                    f"'principal.steward.id'."
                ),
                path='metadata.labels["principal.steward.id"]',
                remediation=(
                    "Add metadata.labels['principal.steward.id'] with the "
                    "employee/user identifier of the data steward."
                ),
            ))

        if steward_id and not steward_email:
            findings.append(Finding(
                severity="warn",
                code="STEWARD_EMAIL_MISSING",
                message=(
                    f"Contract {c.id!r} declares a steward id but no email — "
                    "operations notifications will go nowhere."
                ),
                path='metadata.labels["principal.steward.email"]',
                remediation=(
                    "Add metadata.labels['principal.steward.email'] with the "
                    "team / steward email."
                ),
            ))

        if steward_email and not steward_email.endswith("@my-org.example.com"):
            findings.append(Finding(
                severity="error",
                code="STEWARD_EMAIL_DOMAIN",
                message=(
                    f"Steward email {steward_email!r} must be on the my-org "
                    f"domain (@my-org.example.com)."
                ),
                path='metadata.labels["principal.steward.email"]',
                remediation="Use the steward's official my-org email address.",
            ))

        return [f.to_action() for f in findings]

# tests/test_steward.py
from fluid_sdk.testing import PluginTestHarness, LOCAL_CONTRACT
from my_org_validators.steward import StewardRequired


# Fixture contracts the harness will exercise the validator against
CONTRACT_NO_STEWARD = {
    "metadata": {"id": "p1", "labels": {}},
}
CONTRACT_GOOD_STEWARD = {
    "metadata": {
        "id": "p2",
        "labels": {
            "principal.steward.id": "emp-12345",
            "principal.steward.email": "alice@my-org.example.com",
        },
    },
}
CONTRACT_STEWARD_NO_EMAIL = {
    "metadata": {
        "id": "p3",
        "labels": {"principal.steward.id": "emp-12345"},
    },
}
CONTRACT_WRONG_DOMAIN = {
    "metadata": {
        "id": "p4",
        "labels": {
            "principal.steward.id": "emp-12345",
            "principal.steward.email": "alice@gmail.com",
        },
    },
}


class TestStewardRequired(PluginTestHarness):
    plugin_class = StewardRequired
    # Inherits the standard conformance suite from PluginTestHarness
    # (a Validator-specific subharness is on the roadmap).

    # === Plugin-specific scenarios (you write these) ===

    def test_missing_steward_id_is_error(self):
        actions = self._instantiate().plan(CONTRACT_NO_STEWARD)
        findings = [a for a in actions if a["op"] == "emit_finding"]
        assert any(
            f["params"]["severity"] == "error"
            and f["params"]["code"] == "STEWARD_ID_MISSING"
            for f in findings
        )

    def test_steward_id_present_no_email_is_warning(self):
        actions = self._instantiate().plan(CONTRACT_STEWARD_NO_EMAIL)
        findings = [a for a in actions if a["op"] == "emit_finding"]
        assert any(
            f["params"]["severity"] == "warn"
            and f["params"]["code"] == "STEWARD_EMAIL_MISSING"
            for f in findings
        )

    def test_wrong_email_domain_is_error(self):
        actions = self._instantiate().plan(CONTRACT_WRONG_DOMAIN)
        findings = [a for a in actions if a["op"] == "emit_finding"]
        assert any(
            f["params"]["severity"] == "error"
            and f["params"]["code"] == "STEWARD_EMAIL_DOMAIN"
            for f in findings
        )

    def test_fully_specified_contract_is_clean(self):
        actions = self._instantiate().plan(CONTRACT_GOOD_STEWARD)
        findings = [a for a in actions if a["op"] == "emit_finding"]
        assert findings == []