For the HERE API there's a Python API wrapper but I've not tried this.
There's a good list of other Public Transport APIs here on GitHub.
I see you're in the UK. The UK Government published a data set called NaPTAN which had detailed public transportation data of routes, access points, timetables etc.
However, it's been several years since I last looked ...
I guess from this link that OpenRouteService requires a tuples of coordinates within a parent tuple like:
coords = ((8.34234,48.23424),(8.34423,48.26424))
You have to provide the API the exact format it needs otherwise it will complain.
Also, you are overwriting the csv_coords variable name, by defining it twice
I don't know how your 'ClientCoordinates....
The API's website has its documentation behind a login, so I could not get a written version of this, but based on the slide at 14:13 of this video https://www.youtube.com/watch?v=flJx1rFvccE the directions API needs two pairs of coordinates -- I assume the from and two coordinates. From the examples linked by @umbe1987 in the comments above, it's possible ...