code: def GetFeedMapping(client, feed, placeholder_type):
    
    feed_mapping_service = client.GetService('FeedMappingService', 'v201809')
  
    attribute_mappings = {}
    more_pages = True
  
    selector = {
        'fields': ['FeedMappingId', 'AttributeFieldMappings'],
        'predicates': [
            {
                'field': 'FeedId',
                'operator': 'EQUALS',
                'values': [feed['id']]
            },
            {
                'field': 'PlaceholderType',
                'operator': 'EQUALS',
                'values': [placeholder_type]
            }
        ],
        'paging': {
            'startIndex': 0,
            'numberResults': PAGE_SIZE
        }
    }
  
    while more_pages:
      page = feed_mapping_service.get(selector)
  
      if 'entries' in page:
        # Normally, a feed attribute is mapped only to one field. However, you may
        # map it to more than one field if needed.
        for feed_mapping in page['entries']:
          for attribute_mapping in feed_mapping['attributeFieldMappings']:
            # Since attribute mappings can have multiple values for each key,
            # we use a list to store the values.
            if attribute_mapping['feedAttributeId'] in attribute_mappings:
              attribute_mappings[attribute_mapping['feedAttributeId']].append(
                  attribute_mapping['fieldId'])
            else:
              attribute_mappings[attribute_mapping['feedAttributeId']] = [
                  attribute_mapping['fieldId']]
  
      selector['paging']['startIndex'] += PAGE_SIZE
      more_pages = selector['paging']['startIndex'] < int(page['totalNumEntries'])
  
    return attribute_mappings
docs: Gets the Feed Mapping for a given Feed.
  
    Args:
      client: an AdWordsClient instance.
      feed: the Feed we are retrieving the Feed Mapping for.
      placeholder_type: the Placeholder Type we are looking for.
    Returns:
      A dictionary containing the Feed Mapping.