class_docstr: It's simple wrapper for `AttributeDTO` objects which uses alpha series attributes to fake channels.
  
  Alpha leaderboard doesn't have `ChannelDTO` since it doesn't support channels at all,
  so we do need fake `ChannelDTO` class for backward compatibility with old client's code.
class_docstr_tok: ["It","'s","simple","wrapper","for","`","AttributeDTO","`","objects","which","uses","alpha","series","attributes","to","fake","channels",".","Alpha","leaderboard","does","n't","have","`","ChannelDTO","`","since","it","does","n't","support","channels","at","all",",","so","we","do","need","fake","`","ChannelDTO","`","class","for","backward","compatibility","with","old","client","'s","code","."]
code: def x(self):
      return self._properties.lastStep
  
imports: import abc
  from collections import namedtuple
  from neptune.attributes import constants
  from neptune.internal import operation
  from neptune.internal.backends.api_model import AttributeType
  from neptune.internal.operation import ImageValue
  from neptune.legacy.exceptions import NeptuneException
  from neptune.legacy.internal.channels.channels import ChannelType, ChannelValueType
label_desc: Use image node_id 4 for calling the AlphaChannelDTO obj's underlying member method code with example usage: obj.x() and returns: self