fixup! address code review comments

types/common.d.ts

@@ -18,7 +18,7 @@ export type Options = AnyObject<any>;
 /**
  * Type alias for Node.js callback functions
  */
-export type Callback<T = any> = (err?: Error | null, result?: T) => void;
+export type Callback<T = any> = (err?: any | null, result?: T) => void;
 
 /**
  * Return export type for promisified Node.js async methods.

types/model.d.ts

@@ -242,8 +242,14 @@ export declare class ModelBuilder extends EventEmitter {
   ): ModelBaseClass;
 }
 
+/**
+ * An extension of the built-in Partial<T> type which allows partial values
+ * in deeply nested properties too.
+ */
+export type DeepPartial<T> = { [P in keyof T]?: DeepPartial<T[P]>; };
+
 /**
  * Union export type for model instance or plain object representing the model
  * instance
  */
-export type ModelData<T extends ModelBase = ModelBase> = T | Partial<T>;
+export type ModelData<T extends ModelBase = ModelBase> = T | DeepPartial<T>;