Observable.observeOn() not included in "lite" distribution (contrary to documentation)

[zebulonj]

The library documentation indicates that the .observeOn(...) method of the Observable class is included in the rx.lite distribution (see here). However, a Subject (which is documented to inherit from the Observable class) created from the "lite" distribution does not include the observeOn method as an instance operator.

Version: 4.1.0

Reproduce:

import test from 'tape';

import Rx, { Subject } from 'rx/dist/rx.lite';

test( "rxjs...", sub => {
  sub.test( "...should support the observeOn method via the lite distribution.", assert => {
    assert.plan( 2 );

    const subject = new Subject();
    assert.ok( subject, "A subject should have been instantiated." );
    assert.equal( typeof subject.observeOn, 'function', "The subject should have an observeOn method." );

    assert.end();
  });
});

Output:

✓ rxjs...
⨯ ...should support the observeOn method via the lite distribution.
  not ok 2 The subject should have an observeOn method.
    ---
      operator: equal
      expected: 'function'
      actual:   'undefined'
      at: Test.<anonymous> ([redacted])
    ...

# tests 2
# pass  1
⨯ fail  1

[zebulonj]

Same result if the observable is create using Observable.create(...) or Observable.return(...).

[zebulonj]

Review of repository reveals that observeOn(...) is included in the rx-lite-extras distribution.