def depth
      h = get_ssl(@url_public + "/getboard?product_code=#{@product_code}")
      {
        "asks"       => h["asks"].map{|x| [BigDecimal.new(x["price"].to_s), BigDecimal.new(x["size"].to_s)]},
        "bids"       => h["bids"].map{|x| [BigDecimal.new(x["price"].to_s), BigDecimal.new(x["size"].to_s)]},
        "ltimestamp" => Time.now.to_i,
      }
    end
def depth
      h = get_ssl(@url_public + "/getboard?product_code=#{@product_code}")
      {
        "asks"       => h["asks"].map{|x| [BigDecimal.new(x["price"].to_s), BigDecimal.new(x["size"].to_s)]},
        "bids"       => h["bids"].map{|x| [BigDecimal.new(x["price"].to_s), BigDecimal.new(x["size"].to_s)]},
        "ltimestamp" => Time.now.to_i,
      }
    end
Get order book.
 @abstract
 @return [hash] array of market depth
   asks: [Array] 売りオーダー
      price : [BigDecimal]
      size : [BigDecimal]
   bids: [Array] 買いオーダー
      price : [BigDecimal]
      size : [BigDecimal]
   ltimestamp: [int] ローカルタイムスタンプ