### Question:
KeepFlux extends AbstractParametrizedFlux { @Nonnull public KeepFlux withFunction(@Nonnull final String function) { Arguments.checkNonEmpty(function, "Function"); this.withFunction("fn: (column)", function); return this; } KeepFlux(@Nonnull final Flux source); @Nonnull KeepFlux withColumns(@Nonnull final String[] columns); @Nonnull KeepFlux withColumns(@Nonnull final Collection<String> columns); @Nonnull KeepFlux withFunction(@Nonnull final String function);  }### Answer:
@Test void keepByParameters() { Flux flux = Flux .from("telegraf") .keep() .withFunction("column =~ /inodes*/"); Assertions.assertThat(flux.toString()).isEqualToIgnoringWhitespace("from(bucket:\"telegraf\") |> keep(fn: (column) => column =~ /inodes*/)"); }