from typing import List
from typing import Dict
from typing import Any


def sanitize_pet_field(pets: List[Dict[str, Any]], field: str = "id") -> str:
    """Concatenate pet fields and return them as a string."""
    if len(pets) > 1:
        return ", ".join(str(pet[field]) for pet in pets)
    if len(pets) == 0:
        return ""
    else:
        return pets[0][field]