def filter_sobject_list(sobject_list):
    """
    Takes a list of FeedItem/FeedComment and returns the list with only the fields that we care about,
    with normalized keys.
    """
    sobject_type = sobject_list[0]['attributes']['type'] if sobject_list else None
    fields = ('Body' if sobject_type == 'FeedItem' else 'CommentBody',
              'Id' if sobject_type == 'FeedItem' else 'FeedItemId',
              'ParentId',
              'CreatedById',
              'CreatedDate')
    filtered_sobject_list = [ {key: x[key] for key in fields} for x in sobject_list ]

    for sobject in filtered_sobject_list:
        # Normalize all body fields to be called "Body".
        if 'CommentBody' in sobject:
            sobject['Body'] = sobject.pop('CommentBody')
        # Normalize all feed item ID fields to be called "FeedItemId".
        if 'FeedItemId' not in sobject:
            sobject['FeedItemId'] = sobject.pop('Id')

    return filtered_sobject_list