code: def _get_param(self, section, key, config, default=None):
          
          if section in config and key in config[section]:
              return config[section][key]
          if default is not None:
              return default
          else:
              raise MissingParameter(section, key)
docs: Get configuration parameter "key" from config
          @str section: the section of the config file
          @str key: the key to get
          @dict config: the configuration (dictionnary)
          @str default: the default value if parameter "key" is not present
          @rtype: str (value of config['key'] if present default otherwith