Use this to determine the availability of a Bazel feature in your ruleset. It works under the hood by comparing the Bazel version against a known range in which the feature is available. Example usage:
load("@bazel_features//:features.bzl", "bazel_features")
if bazel_features.toolchains.has_optional_toolchains:
# Do something
The features.bzl
file contains the list of features.