code: def surveys(self):
          
          survey_time_list = list()
          # Extract surveyTimes from /scenario/monitoring/surveys section
          # Using root element instead of xpath to avoid problems with namespaces
          # (root tag was <scenario> prior to schema 32, and then it was switched to <om:scenario>)
          try:
              for item in self.et.find("surveys").findall("surveyTime"):
                  # Converting to float first to allow values like 730.0
                  survey_time_list.append(int(item.text))
          except AttributeError:
              return None
          return survey_time_list
docs: Returns the list of timesteps when survey measures has been captured
          None if xml document is mailformed
          xpath: /scenario/monitoring/survey
          https://github.com/SwissTPH/openmalaria/wiki/GeneratedSchema32Doc#survey-times-time-steps