listCategory() 
This function is part of IconSet class in Iconify Tools.
Function listCategory() lists icons that belong to a category.
Categories are used to filter icons when displaying icon set.
Usage 
Function has the following parameter:
- category, string|IconCategory. Category name or item.
Function returns string[] array of icon names.
Result does not include:
- Hidden icons (and their variations).
- Aliases.
This function automatically updates count property of IconCategory item. If category is empty, category is removed from categories property of icon set.
Example 
example.ts
ts
import { IconSet } from '@iconify/tools';
// Import icon set
const iconSet = new IconSet({
    prefix: 'carbon',
    icons: {
        'add': {
            body: '<path d="M17 15V8h-2v7H8v2h7v7h2v-7h7v-2z" fill="currentColor"/>',
        },
        'arrow-down': {
            body: '<path d="M24.59 16.59L17 24.17V4h-2v20.17l-7.59-7.58L6 18l10 10l10-10l-1.41-1.41z" fill="currentColor"/>',
        },
        'arrow-left': {
            body: '<path d="M14 26l1.41-1.41L7.83 17H28v-2H7.83l7.58-7.59L14 6L4 16l10 10z" fill="currentColor"/>',
        },
        'back-to-top': {
            body: '<path d="M16 14L6 24l1.4 1.4l8.6-8.6l8.6 8.6L26 24z" fill="currentColor"/><path d="M4 8h24v2H4z" fill="currentColor"/>',
        },
        'bookmark-filled': {
            body: '<path d="M24 2H8a2 2 0 0 0-2 2v26l10-5.054L26 30V4a2 2 0 0 0-2-2z" fill="currentColor"/>',
        },
        'caret-down': {
            body: '<path d="M24 12l-8 10l-8-10z" fill="currentColor"/>',
        },
        'caret-left': {
            body: '<path d="M20 24l-10-8l10-8z" fill="currentColor"/>',
        },
    },
    aliases: {
        'plus': {
            parent: 'add',
        },
        'arrow-up': {
            parent: 'arrow-down',
            vFlip: true,
        },
        'arrow-right': {
            parent: 'arrow-left',
            hFlip: true,
        },
        'caret-up': {
            parent: 'caret-down',
            vFlip: true,
        },
        'caret-right': {
            parent: 'caret-left',
            hFlip: true,
        },
    },
    width: 32,
    height: 32,
 });
// Add few categories
 iconSet.toggleCategory('arrow-down', 'Arrows', true);
 iconSet.toggleCategory('arrow-left', 'Arrows', true);
 iconSet.toggleCategory('caret-down', 'Arrows', true);
 iconSet.toggleCategory('caret-left', 'Arrows', true);
 iconSet.toggleCategory('bookmark-filled', 'Bookmarks', true);
 iconSet.toggleCategory('bookmark-filled', 'Filled', true);
// List icons in category
// [ 'arrow-down', 'arrow-left', 'caret-down', 'caret-left' ]
console.log(iconSet.listCategory('Arrows'));
// Rename category using `categories` property
 iconSet.categories.forEach((item) => {
    if (item.title === 'Arrows') {
        item.title = 'Simple Icons';
    }
 });
// List icons in category (no longer exists)
// null
console.log(iconSet.listCategory('Arrows'));