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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 CreateAdGroup(client, campaign_id):
 """Creates a dynamic remarketing campaign. Args: client: an AdWordsClient instance. campaign_id: an int campaign ID. Returns: The ad group that was successfully created. """

  ad_group_service = client.GetService('AdGroupService', 'v201809')

  ad_group = {
      'name': 'Dynamic remarketing ad group',
      'campaignId': campaign_id,
      'status': 'ENABLED'
  }

  operations = [{
      'operator': 'ADD',
      'operand': ad_group
  }]

  return ad_group_service.mutate(operations)['value'][0]