Selection criteria of the returning price data.
    :param list price_data: PriceData filter to specify what market data we wish to receive.
    :param dict ex_best_offers_overrides: define order book depth, rollup method.
    :param bool virtualise: whether to receive virtualised prices also.
    :param bool rollover_stakes: whether to accumulate volume at each price as sum of volume at that price and all better
    prices.

    :returns: price data criteria for market data.
    :rtype: dict

def price_projection(price_data=price_data(), ex_best_offers_overrides=ex_best_offers_overrides(), virtualise=True,
                     rollover_stakes=False):
    """
    Selection criteria of the returning price data.
    :param list price_data: PriceData filter to specify what market data we wish to receive.
    :param dict ex_best_offers_overrides: define order book depth, rollup method.
    :param bool virtualise: whether to receive virtualised prices also.
    :param bool rollover_stakes: whether to accumulate volume at each price as sum of volume at that price and all better
    prices.

    :returns: price data criteria for market data.
    :rtype: dict
    """
    args = locals()
    return {
        to_camel_case(k): v for k, v in args.items() if v is not None
    }