Write a Python function `n_largest_items(lst, n)` that takes in a list `lst` of numbers and an integer `n`. The function should return a list containing the `n` largest items from the input list in descending order.
#### Example Usage
```python [main.nopy]
print(n_largest_items([10, 20, 50, 70, 90, 20, 50, 40, 60, 80, 100], 2))
# Output: [100, 90]
print(n_largest_items([10, 20, 50, 70, 90, 20, 50, 40, 60, 80, 100], 5))
# Output: [100, 90, 80, 70, 60]
print(n_largest_items([10, 20, 50, 70, 90, 20, 50, 40, 60, 80, 100], 3))
# Output: [100, 90, 80]
```
#### Constraints
- The input list will contain at least `n` elements.
- The input list may contain duplicate values.
- The output list should be sorted in descending order.