modify the placeholder attr parser to handle dict/list types

[TroyGarden]

Summary:

context

• to handle complex ph_key for the placeholder like the following:

  (Pdb) arg.op
  'placeholder'
  (Pdb) arg.ph_key
  'event_id_list_features_seqs[marketplace]'

• original workaround is to modify the arg_info in the _start_data_dist

  (Pdb) forward.args
  [ArgInfo(input_attrs=['event_id_list_features_seqs[user_conv_ads_event]'], is_getitems=[False], name=None)]
  (Pdb) attr
  'event_id_list_features_seqs[user_conv_ads_event]'

• according to the ph_key generation, it could be something like A[key][idx].

Differential Revision: D59074268

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D59074268

[facebook-github-bot]

This pull request was exported from Phabricator. Differential Revision: D59074268