def names_by_value(a)
      a = @data[a] if a.is_a?(String) || a.is_a?(Symbol)
      Hash[ a.map { |i| i.reverse } ]
    end
def names_by_value(a)
      a = @data[a] if a.is_a?(String) || a.is_a?(Symbol)
      Hash[ a.map { |i| i.reverse } ]
    end
Converts an options-style nested array into a hash
 for easy name lookup
 @param [Array] a an array like [['name', 'val']]
 @return [Hash] a hash like { val => name }