class Checked
  class Hashs

    def check!
      demand hash?(return!), "...is not a Hash."
    end

    def symbol_keys!
      all_syms = return!.keys.all? { |k| k.is_a?(Symbol) }
      demand all_syms, '...must have all symbol keys.'
    end

  end # === class Hashs
end # === class Checked