working example

the example in the readme does not seems to work.
```sh
trip-flows build \
  --bbox "-74.20303344726562,40.531545551348394,-73.55484008789062,41.017210578228436" \
  --traces ./traces.json
```
There are some files hard written in the source code, can you please provide these files so we can have a working example to build from ?