code: def testPeriod1(self):
      def simple_roc(value1, value2):
          return self.__buildROC([value1, value2], 1)[1]
  
      self.assertTrue(simple_roc(1, 2) == 1)
      self.assertTrue(simple_roc(1, 2) == simple_roc(50, 100))
      self.assertTrue(simple_roc(2, 1) == -0.5)
      self.assertTrue(simple_roc(2, 1) == simple_roc(100, 50))
  
file_path: pyalgotrade/testcases/technical_roc_test.py
imports: from six.moves import xrange
  from .None import common
  from pyalgotrade.technical import roc
  from pyalgotrade import dataseries
label_desc: Use image node_id 3 for calling the ROCTestCase obj's underlying member method code with example usage: obj.testPeriod1() and returns: self