code: public static SpanId fromLowerBase16(CharSequence src, int srcOffset) {
      Utils.checkNotNull(src, "src");
      return new SpanId(BigendianEncoding.longFromBase16String(src, srcOffset));
    }
docs: Returns a {@code SpanId} built from a lowercase base16 representation.
  
  @param src the lowercase base16 representation.
  @param srcOffset the offset in the buffer where the representation of the {@code SpanId}
  begins.
  @return a {@code SpanId} built from a lowercase base16 representation.
  @throws NullPointerException if {@code src} is null.
  @throws IllegalArgumentException if not enough characters in the {@code src} from the {@code
  srcOffset}.
  @since 0.11