* example:
   *
   * {@snippet :
   * CharMatcher.is('a').retainFrom("bazaar")
   * }
   *
   * ... returns {@code "aaa"}.
   */
  public String retainFrom(CharSequence sequence) {
    return negate().removeFrom(sequence);
  }

  /**
   * Returns a string copy of the input character sequence, with each matching BMP character

AAVH,CAAoB3O,OAApB2O,CAA4BC,IAA5BD,QACR,SAGJ,EAPgB,IAqCnBI,GAAqBF,IAAaxQ,OAAO2Q,WAY/BD,GAvChB,WAAsC,IAChCE,YACG,WAAM,SAAA,QAKJD,QAAQE,UAAUC,KAAK,UAAM,KAAA,IAApC,EALW,CAAb,EAqCcJ,CAzBhB,WAAiC,IAC3BK,YACG,WAAM,SAAA,YAGE,UAAM,KAAA,IAAjB,KAHS,CAAb,G3C1BI1P,GAASmP,IAAa,CAAC,EAAExQ,OAAOgR,oBAAPhR,EAA+BS,SAASwQ,YAA1C,EACvBzL,GAASgL,IAAa,UAAUzP,IAAV,CAAeuP,UAAUG,SAAzB,gnB4CItBS,GAAYV,IAAa,WAAWzP,IAAX,CAAgBuP,UAAUG,SAA1B,wKLJzB1B,GAAkBoC,GAAW7G,KAAX6G,CAAiB,CAAjBA,EMKlBC,GAAY,MACV,MADU,WAEL,WAFK,kBAGE,kB...

 - Extended Resources are fully-qualified resource names outside the
 `kubernetes.io` domain. Extended Resource quantities must be integers.
 You can specify any resource name of the form `[aaa.]my-domain.bbb/ccc`
 in place of [Opaque Integer Resources](https://v1-6.docs.kubernetes.io/docs/concepts/configuration/manage-compute-resources-container/#opaque-integer-resources-alpha-feature).