code: def load_master_config(config_dir=None):
      
      config_dir = config_dir or phy_config_dir()
      path = op.join(config_dir, 'phy_config.py')
      # Create a default config file if necessary.
      if not op.exists(path):
          _ensure_dir_exists(op.dirname(path))
          logger.debug("Creating default phy config file at `%s`.", path)
          with open(path, 'w') as f:
              f.write(_default_config(config_dir=config_dir))
      assert op.exists(path)
      return load_config(path)
docs: Load a master Config file from `~/.phy/phy_config.py`.