docs: def get_reward_function(self):
          """
          Returns the reward function as nested dict in the case of table-
          type parameter and a nested structure in case of
          decision diagram parameter
  
          Example
          --------
          >>> reader = PomdpXReader('Test_PomdpX.xml')
          >>> reader.get_reward_function()
          [{'Var': 'reward_rover',
                'Parent': ['action_rover', 'rover_0', 'rock_0'],
                'Type': 'TBL',
                'Parameter': [{'Instance': ['ame', 's1', '*'],
                               'ValueTable': ['10']},
                           ...
                          ]
          }]
          """
          reward_function = []
          for variable in self.network.findall('RewardFunction'):
              for var in variable.findall('Func'):
                  func = defaultdict(list)
                  func['Var'] = var.find('Var').text
                  func['Parent'] = var.find('Parent').text.split()
                  if not var.find('Parameter').get('type'):
                      func['Type'] = 'TBL'
                  else:
                      func['Type'] = var.find('Parameter').get('type')
                  func['Parameter'] = self.get_parameter(var)
                  reward_function.append(func)
  
          return reward_function