Problem with Scheduled Events

Hi guys, 

I am trying to write an algorithm that buy BTCUSD on a series of offsets every year, using .date_rules.year_start(, but i get following errors: 

- Runtime Error: 'NoneType' object is not callable

and

• Backtest Handled Error: BTCUSD: The security does not have an accurate price as it has not yet received a bar of data. Before placing a trade (or using SetHoldings) warm up your algorithm with SetWarmup, or use slice.Contains(symbol) to confirm the Slice object has price before using the data. Data does not necessarily all arrive at the same time so your algorithm should confirm the data is ready before using it. In live trading this can mean you do not have an active subscription to the asset class you're trying to trade. If using custom data make sure you've set the 'Value' property.

Where is the issue? 

# region imports
from AlgorithmImports import *
# endregion

class HipsterFluorescentPinkGoshawk(QCAlgorithm):

    def initialize(self):
        self.set_start_date(2015, 1, 1)
        self.set_cash(100000)
        self.add_crypto("BTCUSD", Resolution.DAILY,Market.KRAKEN)

        self.SetWarmUp(1)    

        self.long_day=[2,3,46,135,154,210,220]
        self.short_day=[170,316]

        for day in self.long_day: 
            self.schedule.on(
                self.date_rules.year_start(day-1),
                self.time_rules.at(15, 0, 0, TimeZones.UTC),
                self._trade('BTCUSD',1)
            )
        
        for day in self.short_day: 
            self.schedule.on(
                self.date_rules.year_start(day-1),
                self.time_rules.at(15, 0, 0, TimeZones.UTC),
                self._trade('BTCUSD',-1)
            )

    def on_data(self, data: Slice):
        self.log(data.time)
        
        #if self.portfolio.cash_book["BTC"].amount > 0:
            #self.liquidate("BTCUSD")
            #return
    
    def _trade(self,symbol,position):
        self.Symbol = symbol
        self.Position = position

        self.set_holdings(self.Symbol,self.Position)