Comment.edit() doesn't work with top level posts

When you try to edit a comment (top level post), you get an error "KeyError: 'parent_author'.

>>> comment.edit(new_body)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/mal/miniconda3/lib/python3.11/site-packages/beem/comment.py", line 748, in edit
    original_post["parent_author"], original_post["parent_permlink"])
    ~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^
  File "/home/mal/miniconda3/lib/python3.11/site-packages/beem/blockchainobject.py", line 210, in __getitem__
    return super(BlockchainObject, self).__getitem__(key)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
KeyError: 'parent_author'

Ultimately, Comment.edit() returns to a call to blockchaininstance.post() which I am able to use directly to work around this issue.