@Override
  public String format(final Schema schema) {
    final String converted = SchemaWalker.visit(schema, new Converter()) + typePostFix(schema);

    return options.contains(Option.AS_COLUMN_LIST)
        ? stripTopLevelStruct(converted)
        : converted;
  }
@Test
  public void shouldFormatOptionalMap() {
    // Given:
    final Schema schema = SchemaBuilder
        .map(Schema.OPTIONAL_STRING_SCHEMA, Schema.OPTIONAL_FLOAT64_SCHEMA)
        .optional()
        .build();

    // Then:
    assertThat(DEFAULT.format(schema), is("MAP<VARCHAR, DOUBLE>"));
    assertThat(STRICT.format(schema), is("MAP<VARCHAR, DOUBLE>"));
  }