Price calculate incorrect in buy side

[pgCanal]

Hi team,

Thanks for the great package!

I found the current price and size calculation for the fill event (SIDE = BUY) in the below links may be wrong at least for Dex V3.

pyserum/pyserum/market/core.py

Lines 104 to 107 in d0938e9

	price = (price_before_fees * self.state.base_spl_token_multiplier()) / (
	self.state.quote_spl_token_multiplier() * event.native_quantity_paid
	)
	size = event.native_quantity_paid / self.state.base_spl_token_multiplier()

The potential update will be. Reference from

https://github.com/project-serum/serum-ts/blob/4cdea04ffbc6fd68392d8f8608ba5c7524007d4e/packages/serum/src/market.ts#L1138-L1164

    if event.event_flags.bid:
        side = Side.BUY
        price_before_fees = (
            event.native_quantity_paid + event.native_fee_or_rebate
            if event.event_flags.maker
            else event.native_quantity_paid - event.native_fee_or_rebate
        )
        price = (price_before_fees * self.state.base_spl_token_multiplier()) / (
        self.state.quote_spl_token_multiplier() * event.native_quantity_released
        )
        size = event.native_quantity_released / self.state.base_spl_token_multiplier()

    else:
        side = Side.SELL
        price_before_fees = (
            event.native_quantity_released - event.native_fee_or_rebate
            if event.event_flags.maker
            else event.native_quantity_released + event.native_fee_or_rebate
        )
    
        price = (price_before_fees * self.state.base_spl_token_multiplier()) / (
            self.state.quote_spl_token_multiplier() * event.native_quantity_paid
        )
        size = event.native_quantity_paid / self.state.base_spl_token_multiplier()

[leofisG]

Hey @pgCanal , do you mind creating a PR for this?