Style fixes (prettier).

index.js

@@ -39,12 +39,18 @@ const wrapFunction = fn =>
         const result = fn.call(this, chunk, encoding);
         if (result && typeof result.then == 'function') {
           // thenable
-          result.then(result => (Chain.sanitize(result, this), callback(null)), error => callback(error));
+          result.then(
+            result => (Chain.sanitize(result, this), callback(null)),
+            error => callback(error)
+          );
           return;
         }
         if (result && typeof result.next == 'function') {
           // generator
-          runAsyncGenerator(result, this).then(() => callback(null), error => callback(error));
+          runAsyncGenerator(result, this).then(
+            () => callback(null),
+            error => callback(error)
+          );
           return;
         }
         Chain.sanitize(result, this);
@@ -83,26 +89,21 @@ const wrapArray = fns =>
   });
 
 // is*NodeStream functions taken from https://github.com/nodejs/node/blob/master/lib/internal/streams/utils.js
-const isReadableNodeStream = obj => !!(obj &&
+const isReadableNodeStream = obj =>
+  obj &&
   typeof obj.pipe === 'function' &&
   typeof obj.on === 'function' &&
   (!obj._writableState || (typeof obj._readableState === 'object' ? obj._readableState.readable : null) !== false) && // Duplex
-  (!obj._writableState || obj._readableState) // Writable has .pipe.
-);
+  (!obj._writableState || obj._readableState); // Writable has .pipe.
 
-const isWritableNodeStream = obj => !!(
+const isWritableNodeStream = obj =>
   obj &&
   typeof obj.write === 'function' &&
   typeof obj.on === 'function' &&
-  (!obj._readableState || (typeof obj._writableState === 'object' ? obj._writableState.writable : null) !== false) // Duplex
-);
+  (!obj._readableState || (typeof obj._writableState === 'object' ? obj._writableState.writable : null) !== false); // Duplex
 
-const isDuplexNodeStream = obj => !!(
-  obj &&
-  (typeof obj.pipe === 'function' && obj._readableState) &&
-  typeof obj.on === 'function' &&
-  typeof obj.write === 'function'
-);
+const isDuplexNodeStream = obj =>
+  obj && typeof obj.pipe === 'function' && obj._readableState && typeof obj.on === 'function' && typeof obj.write === 'function';
 
 class Chain extends Duplex {
   constructor(fns, options) {
@@ -116,11 +117,7 @@ class Chain extends Duplex {
       .filter(fn => fn)
       .map((fn, index, fns) => {
         if (typeof fn === 'function' || fn instanceof Array) return Chain.convertToTransform(fn);
-        if (
-          isDuplexNodeStream(fn) ||
-          (!index && isReadableNodeStream(fn)) ||
-          (index === fns.length - 1 && isWritableNodeStream(fn))
-        ) {
+        if (isDuplexNodeStream(fn) || (!index && isReadableNodeStream(fn)) || (index === fns.length - 1 && isWritableNodeStream(fn))) {
           return fn;
         }
         throw Error('Arguments should be functions, arrays or streams.');