How to use the buildbot.plugins.util.Interpolate function in buildbot

#
# You should have received a copy of the GNU General Public License
# along with GNU Radio; see the file COPYING.  If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.
#

from buildbot.plugins import steps
from buildbot.plugins import util

from config_module import tokens

import os

env = {
    "CCACHE_DIR": util.Interpolate(
        os.path.join("/cache", "%(prop:distro)s", "ccache")
    ),
    "PATH": ["/usr/lib/ccache/", "/usr/lib64/ccache/", "${PATH}"]
}


def build_coverage():
    remove_build = steps.RemoveDirectory("build")
    create_build = steps.MakeDirectory("build")
    cmake_step = steps.CMake(
        path=util.Property("src_dir"),
        definitions=util.Property("cmake_defs", {}),
        options=util.Property("cmake_opts", []),
        workdir="build",
        env=env
    )

def __init__(self, branch):
        super().__init__(
            doStepIf=self._has_the_build_failed,
            workersrc="test-results.xml",
            masterdest=util.Interpolate(
                f"/data/www/buildbot/test-results/{branch}/%(prop:buildername)s/build_%(prop:buildnumber)s.xml"
            ),
            mode=0o755,
        )

def interpolate_constructor(loader, node):
    value = loader.construct_scalar(node)
    return util.Interpolate(value)