def convert_column(column, index)
      value = if converter_arity == 1
                @converter.call(column)
              else
                @converter.call(column, index)
              end
      value.to_sym
    end
def convert_column(column, index)
      value = if converter_arity == 1
                @converter.call(column)
              else
                @converter.call(column, index)
              end
      value.to_sym
    end
Convert the column value
 @param [String, Symbol] column the CSV header column value
 @param [Integer] index the CSV header column index
 @return [Symbol] the converted column