Function getBalanceByAccountId

getBalanceByAccountId(queryable, accountId, assetId): Promise<Balance | null>
Retrieves the balance of a specific asset on the provided account
Parameters
- queryable: Queryable
  object to use when querying the blockchain
- accountId: BufferId
  the account on which to get the balance
- assetId: BufferId
  the asset for which to get the balance
Returns Promise<Balance | null>
The current account balance of the specified asset. Or null if account does not have the asset