Extracting User Data from Fact Schema for Foo Class

class User extends SCH.Class<User>('User')({
  userId: SCH.String,
  userEmail: SCH.String
}){}

export class Fact extends SCH.Class<Fact>(
  "Fact"
)({
  id: SCH.UUID,
  title: SCH.String,
  createdBy: User
}) {}

class User extends SCH.Class<User>('User')({
  userId: SCH.String,
  userEmail: SCH.String
}){}

export class Fact extends SCH.Class<Fact>(
  "Fact"
)({
  id: SCH.UUID,
  title: SCH.String,
  createdBy: User
}) {}

export class Foo extends SCH.Class<Foo>(
  "Foo"
)({
  factId: SCH.UUID,
  factTitle: SCH.propertySignature(SCH.String).pipe(SCH.fromKey('id'),
  factCreatedByUserId: ????
  factCreatedByUserEmail: ????
}) {}

export class Foo extends SCH.Class<Foo>(
  "Foo"
)({
  factId: SCH.UUID,
  factTitle: SCH.propertySignature(SCH.String).pipe(SCH.fromKey('id'),
  factCreatedByUserId: ????
  factCreatedByUserEmail: ????
}) {}