code: def _send(self, cmd: str):
          
          logger.debug('>%s', cmd)
          try:
              self._proc.stdout.flush()
              self._proc.stdin.write(f'{cmd}\n')
          except IOError as e:
              raise SolverError(str(e))
docs: Send a string to the solver.
  
          :param cmd: a SMTLIBv2 command (ex. (check-sat))