Function trailing_stop_calculate 

pub fn trailing_stop_calculate(
    price_increment: Price,
    trigger_px: Option<Price>,
    order: &OrderAny,
    bid: Option<Price>,
    ask: Option<Price>,
    last: Option<Price>,
) -> Result<(Option<Price>, Option<Price>)>

Calculates the new trigger and limit prices for a trailing stop order.

trigger_px is an optional override for the trigger price already carried inside order. If Some(_), it takes priority over the value on the order itself, otherwise the function falls back to the value stored on the order.

Returns

A tuple with the newly-set trigger-price and limit-price (if any). None in either position means the respective price did not improve.

Errors

Returns an error if:

• the order type, trigger type, or trailing offset type is invalid.
• the order lacks a required trigger, trailing offset, trailing offset type, or limit offset.
• the calculated price cannot be represented as a [Price].