docs: private static String extractPemString(JsonObject json, String fieldName, String msgPrefix) throws NetworkConfigurationException {
  
          String path = null;
          String pemString = null;
  
          JsonObject jsonField = getJsonValueAsObject(json.get(fieldName));
          if (jsonField != null) {
              path = getJsonValueAsString(jsonField.get("path"));
              pemString = getJsonValueAsString(jsonField.get("pem"));
          }
  
          if (path != null && pemString != null) {
              throw new NetworkConfigurationException(format("%s should not specify both %s path and pem", msgPrefix, fieldName));
          }
  
          if (path != null) {
              // Determine full pathname and ensure the file exists
              File pemFile = new File(path);
              String fullPathname = pemFile.getAbsolutePath();
              if (!pemFile.exists()) {
                  throw new NetworkConfigurationException(format("%s: %s file %s does not exist", msgPrefix, fieldName, fullPathname));
              }
              try (FileInputStream stream = new FileInputStream(pemFile)) {
                  pemString = IOUtils.toString(stream, "UTF-8");
              } catch (IOException ioe) {
                  throw new NetworkConfigurationException(format("Failed to read file: %s", fullPathname), ioe);
              }
  
          }
  
          return pemString;
      }