## The problem
Issue mollie/mollie-api-python#349 (closed, 6 comments): Passing params like from, sort, or limit to balance.get_transactions() raised UnprocessableEntityError: Non-existent query parameter "params.from" for this API call. The client was mangling the parameter names before sending them. A maintainer acknowledged it as a bug and released version 3.6.1 with the fix, and the reporter updated the package and confirmed it works.
## The fix
If balance.get_transactions(**params) raises UnprocessableEntityError complaining about a non-existent query parameter like params.from, while the same call works with no params, this is a client bug that mangled parameter names, not your code. Upgrade mollie-api-python to 3.6.1 or later; the maintainer shipped the fix there and the reporter verified the upgrade resolves it. If you cannot upgrade immediately, calling get_transactions() with no params works as a stopgap, since the bug only triggered when parameters were passed.
## Notes
Thread: https://github.com/mollie/mollie-api-python/issues/349. Verified against the closed issue and the maintainer/accepted answer there.