public boolean isExplicitHttp1() {
        return this == H1 || this == H1C;
    }
Returns {@code true} if this {@link SessionProtocol} is {@link #H1} or {@link #H1C}.
Note that this method returns {@code false} for {@link #HTTP} and {@link #HTTPS}.
core/src/main/java/com/linecorp/armeria/common/SessionProtocol.java