code: def replace(self, replacements):
          
  
          for old_var, new_var in replacements.items():
              old_var_id = id(old_var)
              if old_var_id in self._object_mapping:
                  # FIXME: we need to check if old_var still exists in the storage
                  old_so = self._object_mapping[old_var_id]  # type: StoredObject
                  self._store(old_so.start, new_var, old_so.size, overwrite=True)
  
          return self
docs: Replace variables with other variables.
  
          :param dict replacements:   A dict of variable replacements.
          :return:                    self