lisa/bisector: improve yaml init code
Use yaml.representer instead of yaml.Representer, and the same for Constructor. That avoids touching the class directly, and multiple YAML loaders and dumpers can coexist in the same process.
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Use yaml.representer instead of yaml.Representer, and the same for Constructor. That avoids touching the class directly, and multiple YAML loaders and dumpers can coexist in the same process.