here is my code, struct CoinModel: Identifiable, Codable {   let id, symbol, name: String   let image: String   let currentPrice: Double   let marketCap, marketCapRank, fullyDilutedValuation: Double?   let totalVolume, high24H, low24H: Int?   let priceChange24H, priceChangePercentage24H, marketCapChange24H, marketCapChangePercentage24H: Double?   let circulatingSupply, totalSupply, maxSupply, ath: Int?   let athChangePercentage: Double?   let athDate: String?   let atl, atlChangePercentage: Double?   let atlDate: String?   let lastUpdated: String?   let sparklineIn7D: SparklineIn7D?   let priceChangePercentage24HInCurrency: Double?   let currentHoldings: Double?       enum CodingKeys: String, CodingKey {     case id, symbol, name, image     case currentPrice = "current_price"     case marketCap = "market_cap"     case marketCapRank = "market_cap_rank"     case fullyDilutedValuation = "fully_diluted_valuation"     case totalVolume = "total_volume"     case high24H = "high_24h"     case low24H = "low_24h"     case priceChange24H = "price_change_24h"     case priceChangePercentage24H = "price_change_percentage_24h"     case marketCapChange24H = "market_cap_change_24h"     case marketCapChangePercentage24H = "market_cap_change_percentage_24h"     case circulatingSupply = "circulating_supply"     case totalSupply = "total_supply"     case maxSupply = "max_supply"     case ath     case athChangePercentage = "ath_change_percentage"     case athDate = "ath_date"     case atl     case atlChangePercentage = "atl_change_percentage"     case atlDate = "atl_date"     case roi     case lastUpdated = "last_updated"     case sparklineIn7D = "sparkline_in_7d"     case priceChangePercentage24HInCurrency = "price_change_percentage_24h_in_currency"     case currentHoldings       }       func updateHoldings(amount: Double) -> CoinModel {     return CoinModel(id: id, symbol: symbol, name: name, image: image, currentPrice: currentPrice, marketCap: marketCap, marketCapRank: marketCapRank, fullyDilutedValuation: fullyDilutedValuation, totalVolume: totalVolume, high24H: high24H, low24H: low24H, priceChange24H: priceChange24H, priceChangePercentage24H: priceChangePercentage24H, marketCapChange24H: marketCapChange24H, marketCapChangePercentage24H: marketCapChangePercentage24H, circulatingSupply: circulatingSupply, totalSupply: totalSupply, maxSupply: maxSupply, ath: ath, athChangePercentage: athChangePercentage, athDate: athDate, atl: atl, atlChangePercentage: athChangePercentage, atlDate: atlDate, lastUpdated: lastUpdated, sparklineIn7D: sparklineIn7D, priceChangePercentage24HInCurrency: priceChangePercentage24HInCurrency, currentHoldings: currentHoldings)   }   var currentHoldingsValue: Double {     return (currentHoldings ?? 0) * currentPrice   }   var rank: Int {     return Int(marketCapRank ?? 0)   }     } // MARK: - SparklineIn7D struct SparklineIn7D: Codable {   let price: [Double]? }