     alias Parcel.Domain.ZoningDistrictLandUseCondition, as: ZoningCondition
 
     [land_use | condition_codes ] = line
-    [_ | columns_zone_codes ] = columns_zone_codes
 
     Stream.zip(condition_codes, columns_zone_codes)
     |> Enum.flat_map(fn {condition_code, column_zone_codes} ->

      ...> "O N"  # real
      ...> ])
      ["GO", "PREDS"]

  This ignores the special case of an empty string (""). Right now we leave in
  the empty string as the first item to preserve the column index of the zone
  groups.

      iex> Mix.Tasks.Parcel.IngestLandUseTable.get_unmapped_zone_groups([
      ...>  "WINGARDIUM",
      ...>  "LEVIOSA",
      ...>  ""   # ignored
      ...> ])
      ["WINGARDIUM", "LEVIOSA"]
  """
  def get_unmapped_zone_groups(zone_groups) do
    actualy_zone_groups = zone_groups -- [""]

    actualy_zone_groups -- Map.keys(@zone_groups_to_zone_codes)
  end

    zone_group_lines = Enum.slice lines, 2..4

    Stream.zip(zone_group_lines)
      |> Stream.drop(1)
      |> Stream.map(&Tuple.to_list/1)
      |> Stream.map(fn(zone_group_parts) -> Enum.join(zone_group_parts, " ") end)
      |> Enum.map(&String.trim/1)
