How to use the finmarketpy.backtest.Backtest function in finmarketpy

def _run_strategy(self, trading_model, asset_df, spot_df, spot_df2, br, contract_value_df, pretty_portfolio_name):

        logger = LoggerManager().getLogger(__name__)

        logger.info("Calculating... " + str(pretty_portfolio_name))

        signal_df = trading_model.construct_signal(spot_df, spot_df2, br.tech_params, br, run_in_parallel=False)

        backtest = Backtest()

        backtest.calculate_trading_PnL(br, asset_df, signal_df, contract_value_df, False)
        ret_stats = backtest.portfolio_pnl_ret_stats()
        stats = str(backtest.portfolio_pnl_desc()[0])

        port = backtest.portfolio_cum().resample('B').mean()
        port.columns = [str(pretty_portfolio_name) + ' ' + stats]

        return port, ret_stats

from findatapy.util.fxconv import FXConv

    # for logging
    from findatapy.util.loggermanager import LoggerManager

    # for signal generation
    from finmarketpy.economics import TechIndicator, TechParams

    # for plotting
    from chartpy import Chart, Style

    logger = LoggerManager().getLogger(__name__)

    import datetime

    backtest = Backtest()
    br = BacktestRequest()
    fxconv = FXConv()

    # get all asset data
    br.start_date = "02 Jan 1990"
    br.finish_date = datetime.datetime.utcnow()
    br.spot_tc_bp = 2.5  # 2.5 bps bid/ask spread
    br.ann_factor = 252

    # have vol target for each signal
    br.signal_vol_adjust = True
    br.signal_vol_target = 0.05
    br.signal_vol_max_leverage = 3
    br.signal_vol_periods = 60
    br.signal_vol_obs_in_year = 252
    br.signal_vol_rebalance_freq = 'BM'

from findatapy.timeseries import Calculations

    # for logging
    from findatapy.util import LoggerManager

    # for signal generation
    from finmarketpy.economics import TechIndicator, TechParams

    # for plotting
    from chartpy import Chart, Style

    logger = LoggerManager().getLogger(__name__)

    import datetime

    backtest = Backtest()
    br = BacktestRequest()
    fxconv = FXConv()

    # get all asset data
    br.start_date = "02 Jan 1990"
    br.finish_date = datetime.datetime.utcnow()
    br.spot_tc_bp = 2.5  # 2.5 bps bid/ask spread
    br.ann_factor = 252

    tech_params = TechParams();
    tech_params.sma_period = 200;
    indicator = 'SMA'
    tech_params.only_allow_longs = True
    # tech_params.only_allow_shorts = True

    # pick EUR/USD