code: def load(self, filepath):
          # type: (str) -> None
          
          try:
              self._config.read(filepath)
              import ast
              self.connection.timeout = \
                  self._config.getint("Connection", "timeout")
              self.connection.verify = \
                  self._config.getboolean("Connection", "verify")
              self.connection.cert = \
                  self._config.get("Connection", "cert")
  
              self.proxies.proxies = \
                  ast.literal_eval(self._config.get("Proxies", "proxies"))
              self.proxies.use_env_settings = \
                  self._config.getboolean("Proxies", "env_settings")
  
              self.redirect_policy.allow = \
                  self._config.getboolean("RedirectPolicy", "allow")
              self.redirect_policy.max_redirects = \
                  self._config.getint("RedirectPolicy", "max_redirects")
  
          except (ValueError, EnvironmentError, NoOptionError):
              error = "Supplied config file incompatible."
              raise_with_traceback(ValueError, error)
          finally:
              self._clear_config()
docs: Load configuration from existing file.
  
          :param str filepath: Path to existing config file.
          :raises: ValueError if supplied config file is invalid.