function assignOwnDefaults(objectValue, sourceValue, key, object) {
	      return (objectValue === undefined || !hasOwnProperty.call(object, key))
	        ? sourceValue
	        : objectValue;
	    }
Used by `_.template` to customize its `_.assign` use.

**Note:** This function is like `assignDefaults` except that it ignores
inherited property values when checking if a property is `undefined`.

@private
@param {*} objectValue The destination object property value.
@param {*} sourceValue The source object property value.
@param {string} key The key associated with the object and source values.
@param {Object} object The destination object.
@returns {*} Returns the value to assign to the destination object.