code: def variable_names(self):
          
          result = []
          names = javabridge.call(self.jobject, "getVariableNames", "()Ljava/util/Set;")
          for name in javabridge.iterate_collection(names):
              result.append(javabridge.to_string(name))
          return result
docs: Returns the names of all environment variables.
  
          :return: the names of the variables
          :rtype: list