===== ISTEM =====
Using the `median` function from Python's standard `statistics` module, write `robust_center(values)` that returns the median of a list of numbers, or None for an empty list.

===== HAM YANIT =====
Certainly! You can create a function called `robust_center` that utilizes Python's standard `statistics` module to calculate the median of a list of numbers. If the list is empty, the function will return `None`. Here's how you can do it:

```python
import statistics

def robust_center(values):
    if not values:
        return None
    return statistics.median(values)

# Example usage:
values = [3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5]
print(robust_center(values))  # Output: 5

empty_list = []
print(robust_center(empty_list))  # Output: None
```

This function first checks if the input list `values` is empty. If it is, it returns `None`. Otherwise, it calculates and returns the median of the list using the `statistics.median` function.