0.2: Accordion group opening event example
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**Primary Actor**: User

**Scope**: Ngx-bootstrap DEMO / BS version 3&4

**Goal**: Show example of event listener, which listen all actions with accordion items

Main success scenario:
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1. User open Accordion demo page
2. User click on Group opening event sub-menu
3. User see 3 accordion items, initially not expanded
4. After click on item without event listener, item is opened and in the browser console - nothing happens
5. After click on item with event listener, item is opened and in the browser console - should be message "Accordion has been opened"

Extensions:
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4a. If item is opened, after click on item without event listener, item is closed and in the browser console - nothing happens
5a. If item is opened, after click on item with event listener, item is closed and in the browser console - should be message "Accordion has been closed"

Variations:
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2*. User scroll to Group opening event sub-menu