code: def current_portfolio_weights(self):
          
          position_values = pd.Series({
              asset: (
                      position.last_sale_price *
                      position.amount *
                      asset.price_multiplier
              )
              for asset, position in self.positions.items()
          })
          return position_values / self.portfolio_value
docs: Compute each asset's weight in the portfolio by calculating its held
          value divided by the total value of all positions.
  
          Each equity's value is its price times the number of shares held. Each
          futures contract's value is its unit price times number of shares held
          times the multiplier.