I keep getting an error message saying VIXY is not in the index.  Is there a way to go about fixing this? Thank you.

import numpy as np
from datetime import datetime
import pandas as pd
import math

class VolTrading(QCAlgorithm):

def __init__(self):
self.previous = None
self.position = None

def Initialize(self):

self.SetStartDate(2007,1,1) #Set Start Date
#self.SetEndDate(2018,10,29) #Set End Date
self.SetCash(10000) #Set Strategy Cash
self.AddEquity("SPY", Resolution.Minute)
self.AddEquity("VIXY", Resolution.Minute)

def OnData(self, data):
history_s = self.History(["SPY"], 2, Resolution.Minute)
last_minute_close_s = history_s.loc["SPY"]["close"][-2]

history_v = self.History(["VIXY"], 2, Resolution.Minute)
last_minute_close_v = history_v.loc["VIXY"]["close"][-2]

self.SPercent = math.log((self.Identity("SPY").Current.Value)/
self.VPercent = math.log((self.Identity("VIXY").Current.Value)/

if self.IsWarmingUp:

if SPercent <= -.01:
if self.position == None:
self.SetHoldings("VIXY", 1)
elif self.position == "SPY":
self.SetHoldings("VIXY", 1)
self.position = "VIXY"

elif VPercent <= -.01:
if self.position == None:
self.SetHoldings("SPY", 1)
elif self.position == "VIXY":
self.SetHoldings("SPY", 1)
self.position = "SPY"