def _validate_conn(self, conn: BaseHTTPConnection) -> None:
        """
        Called right before a request is made, after the socket is created.
        """
        super()._validate_conn(conn)

        # Force connect early to allow us to validate the connection.
        if conn.is_closed:
            conn.connect()

        # TODO revise this, see https://github.com/urllib3/urllib3/issues/2791
        if not conn.is_verified and not conn.proxy_is_verified:
            warnings.warn(
                (
                    f"Unverified HTTPS request is being made to host '{conn.host}'. "
                    "Adding certificate verification is strongly advised. See: "
                    "https://urllib3.readthedocs.io/en/latest/advanced-usage.html"
                    "#tls-warnings"
                ),
                InsecureRequestWarning,
            )

        Called right before a request is made, after the socket is created.
        
src/urllib3/connectionpool.py