[enc] Support trianing continuation.

doc/python/python_api.rst

@@ -43,6 +43,8 @@ Core Data Structure
     :members:
     :show-inheritance:
 
+.. autoclass:: xgboost.core.Categories
+
 Learning API
 ------------
 .. automodule:: xgboost.training

include/xgboost/json.h

@@ -45,8 +45,11 @@ class Value {
     kI8Array = 9,
     kU8Array = 10,
     kI16Array = 11,
-    kI32Array = 12,
-    kI64Array = 13
+    kU16Array = 12,
+    kI32Array = 13,
+    kU32Array = 14,
+    kI64Array = 15,
+    kU64Array = 16,
   };
 
   explicit Value(ValueKind _kind) : kind_{_kind} {}
@@ -192,14 +195,26 @@ using U8Array = JsonTypedArray<std::uint8_t, Value::ValueKind::kU8Array>;
  * @brief Typed UBJSON array for int16_t.
  */
 using I16Array = JsonTypedArray<std::int16_t, Value::ValueKind::kI16Array>;
+/**
+ * @brief Typed UBJSON array for uint16_t.
+ */
+using U16Array = JsonTypedArray<std::uint16_t, Value::ValueKind::kU16Array>;
 /**
  * @brief Typed UBJSON array for int32_t.
  */
 using I32Array = JsonTypedArray<std::int32_t, Value::ValueKind::kI32Array>;
+/**
+ * @brief Typed UBJSON array for uint32_t.
+ */
+using U32Array = JsonTypedArray<std::uint32_t, Value::ValueKind::kU32Array>;
 /**
  * @brief Typed UBJSON array for int64_t.
  */
 using I64Array = JsonTypedArray<std::int64_t, Value::ValueKind::kI64Array>;
+/**
+ * @brief Typed UBJSON array for uint64_t.
+ */
+using U64Array = JsonTypedArray<std::uint64_t, Value::ValueKind::kU64Array>;
 
 class JsonObject : public Value {
  public:

include/xgboost/json_io.h

@@ -143,8 +143,11 @@ class JsonWriter {
   virtual void Visit(I8Array  const* arr);
   virtual void Visit(U8Array const* arr);
   virtual void Visit(I16Array const* arr);
+  virtual void Visit(U16Array const* arr);
   virtual void Visit(I32Array  const* arr);
+  virtual void Visit(U32Array  const* arr);
   virtual void Visit(I64Array  const* arr);
+  virtual void Visit(U64Array  const* arr);
   virtual void Visit(JsonObject const* obj);
   virtual void Visit(JsonNumber const* num);
   virtual void Visit(JsonInteger const* num);

python-package/pyproject.toml

@@ -59,7 +59,7 @@ follow_imports = "silent"
 
 [tool.pylint.main]
 ignore = ["tests"]
-extension-pkg-whitelist = ["numpy"]
+extension-pkg-whitelist = ["numpy", "cuda"]
 disable = [
     "import-error",
     "attribute-defined-outside-init",