4.2: Collapse events example
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**Primary Actor**: User

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

**Goal**: Show user how to handle events with collapse

Main success scenario:
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1. User opens Collapse demo page
2. User clicks on Events sub-menu
3. User see clickable "Toggle collapse" button
4. User see div block with "Some content" and div block with "Event: expanded"
5. When user clicks on "Toggle collapse", then "Some content" disappear and user see "Event: collapsed"
6. When user clicks on "Toggle collapse" second time, then "Some content" and div block with "Event: expanded" appear

Variations:
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2*. User scrolls to Events sub-menu