Shapley for conv_value as frequency

While using the parameter conv_value as a frequency metric, the Shapley's results doesn't work.

Start by locating the Shapley implementation and tracing how the conv_value parameter is handled when it represents frequency rather than another metric. Reproduce the reported failure with a frequency-based conv_value, then confirm that the Shapley's results work correctly for that input.

Written by the indexing model from the issue text.