In their paper Lepowsky and Mcmollum sketch theory of weights in a more general setting. Here is their definition of a weight space:
If $A$ is a subset of $\mathfrak g$ and $\lambda$ is a function from $A$ into $k$, $V^{\lambda}_A$ is the set of $x\in\mathfrak g$ such that some power of $\pi(a)-\lambda(a)$ annihilates $x$ for all $a\in A$. The function $\lambda$ such that $A$ into $k$, $V^{\lambda}_A \neq 0$ is called aweight vector.
here $\mathfrak g$ is a lie algebra over a field $k$ and $\pi: \mathfrak g \rightarrow End(V) $ a representation of $\mathfrak g$ on a vctor space $V$.
My question : Shouldn't $V^{\lambda}_A $ be the set of $x\in V$ instead of $x\in\mathfrak g$ in the first line?