def get_data_type(data) # :nodoc:
      # Check for no data in the series.
      return 'none' unless data
      return 'none' if data.empty?
      return 'multi_str' if data.first.kind_of?(Array)

      # If the token isn't a number assume it is a string.
      data.each do |token|
        next unless token
        return 'str' unless token.kind_of?(Numeric)
      end

      # The series data was all numeric.
      'num'
    end
def get_data_type(data) # :nodoc:
      # Check for no data in the series.
      return 'none' unless data
      return 'none' if data.empty?
      return 'multi_str' if data.first.kind_of?(Array)

      # If the token isn't a number assume it is a string.
      data.each do |token|
        next unless token
        return 'str' unless token.kind_of?(Numeric)
      end

      # The series data was all numeric.
      'num'
    end
Find the overall type of the data associated with a series.

 TODO. Need to handle date type.