fix logging issue (if session was not restart between runs, log.txt was not recreated)

Author: sokrypton

AlphaFold2.ipynb

@@ -341,9 +341,10 @@
         "      plt.close()\n",
         "\n",
         "result_dir = jobname\n",
-        "if 'logging_setup' not in globals():\n",
-        "    setup_logging(Path(os.path.join(jobname,\"log.txt\")))\n",
-        "    logging_setup = True\n",
+        "log_filename = os.path.join(jobname,\"log.txt\")\n",
+        "if not os.path.isfile(log_filename) or 'logging_setup' not in globals():\n",
+        "  setup_logging(Path(log_filename))\n",
+        "  logging_setup = True\n",
         "\n",
         "queries, is_complex = get_queries(queries_path)\n",
         "model_type = set_model_type(is_complex, model_type)\n",