Should FungibleTokenBuilder and NonFungibleTokenBuilder heldBy function receive a Party ?

[TywinLannister1313]

This is a small thing I noticed with the new FungibleTokenBuilder and NonFungibleTokenBuilder classes. I'm not sure if it matters but I think it would cause some issues if you wanted to use them with AnonymousParty?

The holder parameter for FungibleToken and NonFungibleToken is AbstractParty:

open class FungibleToken @JvmOverloads constructor(
        override val amount: Amount<IssuedTokenType>,
        override val holder: AbstractParty,
        override val tokenTypeJarHash: SecureHash? = amount.token.tokenType.getAttachmentIdForGenericParam()
) : FungibleState<IssuedTokenType>, AbstractToken, QueryableState {

Whereas the heldBy function in the new builders is Party:

    fun heldBy(party: Party): FungibleTokenBuilder = this.apply {
        this.holder = party
    }