code: def dependents_of(self, address):
      
      assert address in self._target_by_address, (
        'Cannot retrieve dependents of {address} because it is not in the BuildGraph.'
        .format(address=address)
      )
      return self._target_dependees_by_address[address]
docs: Returns the addresses of the targets that depend on the target at `address`.
  
      This method asserts that the address given is actually in the BuildGraph.
  
      :API: public