2つのリストを受け取り、新しいリストを返すPython関数を記述してください
list_a = [1, 2, 3] 
list_b = [4, 5, 6]
def merge_lists(list_a, list_b):
    """Merges two given lists into a new list."""
    new_list = list_a + list_b
    return new_list

list_a = [1, 2, 3] 
list_b = [4, 5, 6]

merged_list = merge_lists(list_a, list_b)
print(merged_list) # Output: [1, 2, 3, 4, 5, 6]