class_docstr: A basic RL graph manager creates the common scheme of RL where there is a single agent which interacts with a
  single environment.
code: def log_signal(self, signal_name, value):
      self.level_managers[0].agents[
          "agent"
      ].agent_logger.create_signal_value(signal_name, value)
  
file_path: coach/rl_coach/graph_managers/basic_rl_graph_manager.py
imports: from typing import Tuple, List
  from rl_coach.base_parameters import AgentParameters, VisualizationParameters, TaskParameters, PresetValidationParameters
  from rl_coach.environments.environment import EnvironmentParameters, Environment
  from rl_coach.filters.filter import NoInputFilter, NoOutputFilter
  from rl_coach.graph_managers.graph_manager import GraphManager, ScheduleParameters
  from rl_coach.level_manager import LevelManager
  from rl_coach.utils import short_dynamic_import
label_desc: Use image node_id 3 for calling the BasicRLGraphManager obj's underlying member method code with example usage: obj.log_signal(signal_name, value) without return types