FieldType:
    | "functionRecord"
    | "function"
    | "record"
    | "variant"
    | "tuple"
    | "optional"
    | "vector"
    | "table"
    | "blob"
    | "recursive"
    | "unknown"
    | "text"
    | "number"
    | "principal"
    | "boolean"
    | "null"