public static Builder builder() {
        return new Builder();
    }
@Test
    void testPrimaryKeyNullableColumn() {
        assertThatThrownBy(
                        () ->
                                TableSchema.builder()
                                        .field("f0", DataTypes.BIGINT())
                                        .primaryKey("pk", new String[] {"f0"})
                                        .build())
                .isInstanceOf(ValidationException.class)
                .hasMessage("Could not create a PRIMARY KEY 'pk'. Column 'f0' is nullable.");
    }