refactor: use assertion utility

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---

Author: kgryte

lib/node_modules/@stdlib/ndarray/base/dtype-enum2str/lib/main.js

@@ -20,6 +20,7 @@
 
 // MODULES //
 
+var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
 var objectInverse = require( '@stdlib/utils/object-inverse' );
 var enumeration = require( '@stdlib/ndarray/dtypes' ).enum;
 
@@ -50,7 +51,7 @@ var hash = objectInverse( enumeration(), {
 */
 function enum2str( dtype ) {
 	var v = hash[ dtype ];
-	return ( typeof v === 'string' ) ? v : null; // note: we include this guard to prevent walking the prototype chain
+	return ( isString( v ) ) ? v : null; // note: we include this guard to prevent walking the prototype chain
 }