This is $\bar{\partial}$-Poincaré lemma: Given a holomorphic funtion $f:U\subset \mathbb{C} \to \mathbb{C}$ ,locally on $U$ there is a holomorphic function $g$ such that : $\frac{\partial g}{\partial \bar z}=f$
The author says that this is a local statement so we may assume $f$ with compact support and defined on the whole plane $\mathbb{C}$, my question is why she says that... thanks.
*Added*
$f,g$ are suppose to be $C^k$ not holomorphic, by definition $\frac{\partial g}{\partial \bar z}=0$ if $g$ were holomorphic...