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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def GetCampaignFeeds(client, feed, placeholder_type):
 """Get a list of Feed Item Ids used by a campaign via a given Campaign Feed. Args: client: an AdWordsClient instance. feed: a Campaign Feed. placeholder_type: the Placeholder Type. Returns: A list of Feed Item Ids. """

  campaign_feed_service = client.GetService('CampaignFeedService', 'v201809')

  campaign_feeds = []
  more_pages = True

  selector = {
      'fields': ['CampaignId', 'MatchingFunction', 'PlaceholderTypes'],
      'predicates': [
          {
              'field': 'Status',
              'operator': 'EQUALS',
              'values': ['ENABLED']
          },
          {
              'field': 'FeedId',
              'operator': 'EQUALS',
              'values': [feed['id']]
          },
          {
              'field': 'PlaceholderTypes',
              'operator': 'CONTAINS_ANY',
              'values': [placeholder_type]
          }
      ],
      'paging': {
          'startIndex': 0,
          'numberResults': PAGE_SIZE
      }
  }

  while more_pages:
    page = campaign_feed_service.get(selector)

    if 'entries' in page:
      campaign_feeds.extend(page['entries'])

    selector['paging']['startIndex'] += PAGE_SIZE
    more_pages = selector['paging']['startIndex'] < int(page['totalNumEntries'])

  return campaign_feeds