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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 clear_unforced_dependencies(self):
 """Remove all dependencies not forced by a comment. This is useful when existing analysis can infer exactly what the correct dependencies should be. Typical use is to call `clear_unforced_dependencies`, then call `add_dependency` for each dependency inferred from analysis. The resulting dependency set should be the pruned set of all dependencies, plus dependencies hand forced by a user comment. """

    self._dependencies_by_address = dict(
      (address, dep) for address, dep in self._dependencies_by_address.items()
      if dep.has_comment()
    )