Lullaby is an adorable composition by French pianist and composer Isidor Philipp and piece no. 93 in Russian School of Piano Playing, the method book I'm using to learn (self-teach) piano.
Not wanting to throw shade at anyone (but already doing it): I honestly love that the Russian method is full of those small pieces, études, miniatures, all original pieces (and not some ridiculous arrangements of dubious taste, like you find in most method books). I think it really says something about the quality of their musical education.
On the surface, just like any other method, it is about learning an instrument and learning to play the right note at the right time. However, it goes much deeper than the traditional French/Classical school of piano (which is the default method people use). The Russian/Romantic school is mostly about expressiveness, musicality, about using technique to achieve artistry.
Isidor Philipp (1863 — 1958) was a French pianist, composer, pedagogue and a child prodigy at the piano! https://en.wikipedia.org/wiki/Isidor_Philipp
Sheet music for this piece:
Book Russian School of Piano Playing book 1 part II (Hal Leonard)