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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def cmd_build(conf: Config, run_tests: bool=False):
 """Build requested targets, and their dependencies."""

    build_context = BuildContext(conf)
    populate_targets_graph(build_context, conf)
    build_context.build_graph(run_tests=run_tests)
    build_context.write_artifacts_metadata()