code: def add_precip_file(self, precip_file_path, interpolation_type=None):
          
          # precip file read in
          self._update_card('PRECIP_FILE', precip_file_path, True)
  
          if interpolation_type is None:
              # check if precip type exists already in card
              if not self.project_manager.getCard('RAIN_INV_DISTANCE') \
                      and not self.project_manager.getCard('RAIN_THIESSEN'):
                  # if no type exists, then make it theissen
                  self._update_card('RAIN_THIESSEN', '')
          else:
              if interpolation_type.upper() not in self.PRECIP_INTERP_TYPES:
                  raise IndexError("Invalid interpolation_type {0}".format(interpolation_type))
              interpolation_type = interpolation_type.upper()
  
              if interpolation_type == "INV_DISTANCE":
                  self._update_card('RAIN_INV_DISTANCE', '')
                  self.project_manager.deleteCard('RAIN_THIESSEN', self.db_session)
              else:
                  self._update_card('RAIN_THIESSEN', '')
                  self.project_manager.deleteCard('RAIN_INV_DISTANCE', self.db_session)
docs: Adds a precip file to project with interpolation_type