The literature of the Post-colonialists encompasses any texts which focus upon races, cultures, and the idea of identity after the gaining of independence. This literature is not, necessarily, limited to only countries which have gained independence from other oppressive and controlling governments, but the colonization of any area throughout time.
Postcolonial literature, most famously, comes out of America, Africa, The Middle East, and Asia. In all of these areas, people have banded together to fight against the oppression of a governing power to declare their freedom. When successful, the "country" maintains colonization. Other times, the people may not be successful at removing oppressive power, but that does not take away the fact that the literature of the period can be (and is) considered Postcolonial.
Given that Postcolonial texts are derived from the fact that people are tired of oppression, sometimes brutal oppression, any text which depicts a desire and movement against the oppressive power is considered Postcolonial.