code: def size(self):
          '''Number of elements in the :class:`Structure`.'''
          if self.cache.cache is None:
              return self.read_backend_structure().size()
          else:
              return len(self.cache.cachef size(self):
          '''Number of elements in the :class:`Structure`.'''
          if self.cache.cache is None:
              return self.read_backend_structure().size()
          else:
              return len(self.cache.cache)
docs: Number of elements in the :class:`Structure`.