code: def _get_error_values(self, startingPercentage, endPercentage, startDate, endDate):
          
          if startDate is not None:
              possibleDates = filter(lambda date: date >= startDate, self._errorDates)
              if 0 == len(possibleDates):
                  raise ValueError("%s does not represent a valid startDate." % startDate)
  
              startIdx = self._errorDates.index(min(possibleDates))
          else:
              startIdx = int((startingPercentage * len(self._errorValues)) / 100.0)
  
          if endDate is not None:
              possibleDates = filter(lambda date: date <= endDate, self._errorDates)
              if 0 == len(possibleDates):
                  raise ValueError("%s does not represent a valid endDate." % endDate)
  
              endIdx = self._errorDates.index(max(possibleDates)) + 1
          else:
              endIdx = int((endPercentage * len(self._errorValues)) / 100.0)
  
          return self._errorValues[startIdx:endIdx]
docs: Gets the defined subset of self._errorValues.
  
          Both parameters will be correct at this time.
  
          :param float startingPercentage: Defines the start of the interval. This has to be a value in [0.0, 100.0].
              It represents the value, where the error calculation should be started.
              25.0 for example means that the first 25% of all calculated errors will be ignored.
          :param float endPercentage:    Defines the end of the interval. This has to be a value in [0.0, 100.0].
              It represents the value, after which all error values will be ignored. 90.0 for example means that
              the last 10% of all local errors will be ignored.
          :param float startDate: Epoch representing the start date used for error calculation.
          :param float endDate: Epoch representing the end date used in the error calculation.
  
          :return:    Returns a list with the defined error values.
          :rtype: list
  
          :raise:    Raises a ValueError if startDate or endDate do not represent correct boundaries for error calculation.