docs: def petl(self, *args, **kwargs):
          """Return a PETL source object"""
          import petl
  
          t = self.resolved_url.get_resource().get_target()
  
          if t.target_format == 'txt':
              return petl.fromtext(str(t.fspath), *args, **kwargs)
          elif t.target_format == 'csv':
              return petl.fromcsv(str(t.fspath), *args, **kwargs)
          else:
              raise Exception("Can't handle")