Solve the programming task below in a Python markdown code block.
In Russia regular bus tickets usually consist of 6 digits. The ticket is called lucky when the sum of the first three digits equals to the sum of the last three digits. Write a function to find out whether the ticket is lucky or not. Return true if so, otherwise return false. Consider that input is always a string. Watch examples below.
Also feel free to reuse/extend the following starter code:
```python
def is_lucky(ticket):
```