What are themes depicted in Maya Angelou's poem "I Know Why the Caged Bird Sings"?

The free bird leaps
on the back of the win
and
floats downstream
till the current ends
and dips his wings
in the
orange sun rays
and dares to claim the
sky.

[...]

The caged bird sings
with fearful
trill
of the things unknown
but longed for still
and is tune is
heard
on the distant hill for the caged bird
sings of freedom

The two most prominent themes are those of (1) freedom versus
oppression and (2) duality. Angelou starts her poem (which bears the same title as her
first autobiographical book ) with a contrast between the free bird that "leaps
/ on the...