code: def reverse_dependencies(self, ireqs):
          
          ireqs_as_cache_values = [self.as_cache_key(ireq) for ireq in ireqs]
          return self._reverse_dependencies(ireqs_as_cache_values)
docs: Returns a lookup table of reverse dependencies for all the given ireqs.
  
          Since this is all static, it only works if the dependency cache
          contains the complete data, otherwise you end up with a partial view.
          This is typically no problem if you use this function after the entire
          dependency tree is resolved.