fix(hand edit): keep model in CategoriesOptions

Source/NaturalLanguageUnderstandingV1/Models/CategoriesOptions.swift

@@ -1,4 +1,4 @@
-/**
+  /**
  * (C) Copyright IBM Corp. 2017, 2020.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
@@ -33,28 +33,39 @@ public struct CategoriesOptions: Codable, Equatable {
      */
     public var limit: Int?
 
+    /**
+     Enter a [custom
+     model](https://cloud.ibm.com/docs/services/natural-language-understanding?topic=natural-language-understanding-customizing)
+     ID to override the standard categories model.
+     */
+    public var model: String?
+
     // Map each property name to the key that shall be used for encoding/decoding.
     private enum CodingKeys: String, CodingKey {
         case explanation = "explanation"
         case limit = "limit"
+        case model = "model"
     }
 
     /**
      Initialize a `CategoriesOptions` with member variables.
-
      - parameter explanation: Set this to `true` to return explanations for each categorization. **This is available
        only for English categories.**.
      - parameter limit: Maximum number of categories to return.
-
+     - parameter model: Enter a [custom
+       model](https://cloud.ibm.com/docs/services/natural-language-understanding?topic=natural-language-understanding-customizing)
+       ID to override the standard categories model.
      - returns: An initialized `CategoriesOptions`.
      */
     public init(
         explanation: Bool? = nil,
-        limit: Int? = nil
+        limit: Int? = nil,
+        model: String? = nil
     )
     {
         self.explanation = explanation
         self.limit = limit
+        self.model = model
     }
 
 }