Retrieves a list of regions.
list(profileId)
  Retrieves a list of regions.
Args:
  profileId: string, User profile ID associated with this request. (required)
Returns:
  An object of the form:
    { # Region List Response
    "regions": [ # Region collection.
      { # Contains information about a region that can be targeted by ads.
        "kind": "dfareporting#region", # Identifies what kind of resource this is. Value: the fixed string "dfareporting#region".
        "countryDartId": "A String", # DART ID of the country to which this region belongs.
        "name": "A String", # Name of this region.
        "countryCode": "A String", # Country code of the country to which this region belongs.
        "regionCode": "A String", # Region code.
        "dartId": "A String", # DART ID of this region.
      },
    ],
    "kind": "dfareporting#regionsListResponse", # Identifies what kind of resource this is. Value: the fixed string "dfareporting#regionsListResponse".
  }