callFunction<T>  method 
Executes a view function from an Aptos module.
entry defines the function to call, and ledgerVersion (optional)
specifies the ledger version to query against.
Implementation
Future<List<T>> callFunction<T>(AptosTransactionEntryFunction entry,
    {BigInt? ledgerVersion}) {
  return provider.request(AptosRequestExecuteViewFunctionOfaModule<T>.bcs(
      entry: entry, ledgerVersion: ledgerVersion));
}