code: def _random_subprocessor(self):
          
          deletion = set()
          for e in self._evil:
              if e[0] in deletion or e[1] in deletion:
                  continue
              deletion.add(choice(e))
          return self._subprocessor(deletion)
docs: Creates a random subprocessor where there is a coupler between
          every pair of working qubits on opposite sides of the same cell.
          This is guaranteed to be minimal in that adding a qubit back in
          will reintroduce a bad coupler, but not to have minimum size.
  
          OUTPUT:
              an :class:`eden_processor` instance