code: def get_file(self, latitude, longitude):
          
          file_name = self.get_file_name(latitude, longitude)
  
          if not file_name:
              return None
  
          if (file_name in self.files):
              return self.files[file_name]
          else:
              data = self.retrieve_or_load_file_data(file_name)
              if not data:
                  return None
  
              result = GeoElevationFile(file_name, data, self)
  
              # Store file (if in batch mode, just keep most recent)
              if self.batch_mode:
                  self.files = {file_name: result}
              else:
                  self.files[file_name] = result
  
              return result
docs: If the file can't be found -- it will be retrieved from the server.