code: def get_addr_spec(value):
      
      addr_spec = AddrSpec()
      token, value = get_local_part(value)
      addr_spec.append(token)
      if not value or value[0] != '@':
          addr_spec.defects.append(errors.InvalidHeaderDefect(
              "add-spec local part with no domain"))
          return addr_spec, value
      addr_spec.append(ValueTerminal('@', 'address-at-symbol'))
      token, value = get_domain(value[1:])
      addr_spec.append(token)
      return addr_spec, value
docs: addr-spec = local-part "@" domain