Defining a Struct with Fixed Keys and Dynamic Index Signatures in TypeScript

Schema.Struct(
    {
        mandatory: Schema.NonEmpty,
        mandatory2: Schema.NonEmpty,
        mandatory3: Schema.OptionFromNullishOr(Schema.Date, undefined),
    },
    Schema.Record(
        Schema.NonEmpty,
        Schema.OptionFromNullishOr(Schema.NonEmpty, undefined),
    ),
)

            Property 'mandatory' is incompatible with index signature.
              Type 'string' is not assignable to type 'Option<string>'.