obalance_record      pending_chain_state::get_balance_record( const balance_id_type& balance_id )const
 {
    auto itr = balances.find( balance_id );
    if( itr != balances.end() ) 
      return itr->second;
    else if( _prev_state ) 
      return _prev_state->get_balance_record( balance_id );
    return obalance_record();
 }
obalance_record pending_chain_state::get_balance_record( const balance_id_type& balance_id )const
{
    chain_interface_ptr prev_state = _prev_state.lock();
    auto itr = balances.find( balance_id );
    if( itr != balances.end() )
        return itr->second;
    else if( prev_state )
        return prev_state->get_balance_record( balance_id );
    return obalance_record();
}