     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} ->

  Rows at index 2 through 4 include identifiers of groups of zones:

    ,          ,....
    Agriculture, Residential,....
    AG   ,  RS280   , ...
    and   , thru   , ...
    AR2a  , RS3.75 , ...

  We translate these three lines into a single list of groups, e.g.
  ["AG and AR2a", "RS280 thru RS3.75"].  This can be used with
  @zone_groups_to_zone_codes to translate the table into information per
  zone code, even though we only receive information per zone group.

  Note that these come back preserving the order of the columns they are in.

  ## Examples
  A basic example:

      iex> Mix.Tasks.Parcel.IngestLandUseTable.get_zone_groups([
      ...>   ["Ignore", "these"],
      ...>   ["First", "two", "rows"],
      ...>   ["AG", "RS80"],
      ...>   ["and", "thru"],
      ...>   ["AR2a", "RS3.75-A"]
      ...> ])
      ["AG and AR2a", "RS80 thru RS3.75-A"]


      ...> "O N"  # real
      ...> ])
      ["GO", "PREDS"]
  """
  def get_unmapped_zone_groups(zone_groups) do
    actualy_zone_groups = zone_groups

    actualy_zone_groups -- Map.keys(@zone_groups_to_zone_codes)
  end
