Write a function that flattens an `Array` of `Array` objects into a flat `Array`.  Your function must only do one level of flattening.
```python
flatten [1,2,3] # => [1,2,3]
flatten [[1,2,3],["a","b","c"],[1,2,3]]  # => [1,2,3,"a","b","c",1,2,3]
flatten [[[1,2,3]]] # => [[1,2,3]]
```
def flatten(lst):
    return [item for sublist in [seq if isinstance(seq, list) else [seq] for seq in lst] for item in sublist]
def flatten(lst):
    return [item for sublist in [seq if isinstance(seq, list) else [seq] for seq in lst] for item in sublist]