Fix lint errors

Author: gpahal

src/clientStub.ts

@@ -123,7 +123,7 @@ export class DgraphClientStub {
     }
 
     public health(): Promise<string> {
-        return fetch(this.getURL("health"), {
+        return fetch(this.getURL("health"), { // tslint:disable-line no-unsafe-any
             method: "GET",
         })
             .then((response: { status: number; text(): string }) => {
@@ -136,7 +136,7 @@ export class DgraphClientStub {
 
     private callAPI<T>(path: string, config: {}): Promise<T> {
         const url = this.getURL(path);
-        return fetch(url, config)
+        return fetch(url, config) // tslint:disable-line no-unsafe-any
             .then((response: { status: number; json(): T }) => {
                 if (response.status >= 300 || response.status < 200) {
                     throw new Error(`Invalid status code = ${response.status}`);

src/errors.ts

@@ -2,24 +2,30 @@ export const ERR_NO_CLIENTS = new Error("No clients provided in DgraphClient con
 export const ERR_FINISHED = new Error("Transaction has already been committed or discarded");
 export const ERR_ABORTED = new Error("Transaction has been aborted. Please retry");
 
+/**
+ * CustomError is base class used for defining custom error classes.
+ */
 export class CustomError extends Error {
     public readonly name: string;
 
     constructor(message?: string) {
         super(message);
+
+        // tslint:disable no-any no-unsafe-any
         this.name = new.target.name;
 
         // fix the extended error prototype chain because typescript __extends implementation can't
-        const setPrototypeOf: Function = (<any>Object).setPrototypeOf; // tslint:disable-line no-any
-        setPrototypeOf
+        const setPrototypeOf: Function = (<any>Object).setPrototypeOf;
+        setPrototypeOf != null
             ? setPrototypeOf(this, new.target.prototype)
-            : ((<any>this).__proto__ = new.target.prototype); // tslint:disable-line no-any
+            : ((<any>this).__proto__ = new.target.prototype);
 
         // try to remove contructor from stack trace
-        const captureStackTrace: Function = (<any>Error).captureStackTrace; // tslint:disable-line no-any
-        if (captureStackTrace) {
+        const captureStackTrace: Function = (<any>Error).captureStackTrace;
+        if (captureStackTrace != null) {
             captureStackTrace(this, this.constructor);
         }
+        // tslint:enable no-any no-unsafe-any
     }
 }
 
@@ -28,6 +34,9 @@ export interface APIResultError {
     message: string;
 }
 
+/**
+ * APIError represents an error returned by Dgraph's HTTP server API.
+ */
 export class APIError extends CustomError {
     public readonly url: string;
     public readonly errors: APIResultError[];