code: def from_snl(cls, snl):
          
          hist = []
          for h in snl.history:
              d = h.description
              d['_snl'] = {'url': h.url, 'name': h.name}
              hist.append(d)
          return cls(snl.structure, history=hist)
docs: Create TransformedStructure from SNL.
  
          Args:
              snl (StructureNL): Starting snl
  
          Returns:
              TransformedStructure