code: public String getKeyOrDefault(String key) {
          if (StringUtils.isBlank(key)) {
              if (this.hasDefaultEnvironment()) {
                  return defaultEnvironment;
              } else {
                  throw new MultiEnvSupportException("[environment] property is mandatory and can't be empty");
              }
          }
          if (map.containsKey(key)) {
              return key;
          }
          if (this.hasTemplateEnvironment()) {
              return this.templateEnvironment;
          }
          LOG.error("Failed to find environment [{}] in {}", key, this.keySet());
          throw new MultiEnvSupportException(String.format(
                  "Failed to find configuration for environment %s", key));
      }
docs: Returns the key, if that specified key is mapped to something
  
  @param key - environment name
  @return String