code: def testTrend(self):
      trend = self.__buildTrend([1, 2, 3, 2, 1], 3, 0, 0)
      self.assertEqual(trend[0], None)
      self.assertEqual(trend[1], None)
      self.assertEqual(trend[2], True)
      self.assertEqual(trend[3], None)
      self.assertEqual(trend[4], False)
  
      self.assertEqual(len(trend.getDateTimes()), 5)
      for i in range(len(trend)):
          self.assertEqual(trend.getDateTimes()[i], None)
  
file_path: pyalgotrade/testcases/technical_trend_test.py
imports: from .None import common
  from pyalgotrade.technical import linreg
  from pyalgotrade import dataseries
label_desc: Use image node_id 2 for calling the TrendTest obj's underlying member method code with example usage: obj.testTrend() without return types