OpenMetrics support for textfile collector

Currently prometheus_client.exposition.write_to_textfile doesn't support the OpenMetrics text format, which I'm addressing with this (private) hack:

from prometheus_client.openmetrics.exposition import (
    generate_latest as generate_latest_openmetrics,
)
from prometheus_client.registry import CollectorRegistry

def write_openmetrics_to_textfile(path: str, registry: CollectorRegistry) -> None:
    """
    Fork of `prometheus_client.exposition.write_to_textfile`, as the project
    didn't provide an OpenMetrics variant of this helper function.
    """
    with open(path, "wb") as fp:
        fp.write(generate_latest_openmetrics(registry))

Would your project be interested in a non-hacky (as is the case above) OpenMetrics support for textfile collector?

Start at prometheus_client.exposition.write_to_textfile and compare its behavior with prometheus_client.openmetrics.exposition.generate_latest. Determine how the helper should expose OpenMetrics output while preserving the existing textfile collector behavior. Done means the supported helper writes valid OpenMetrics text for the provided registry and is covered by the project's relevant tests.