In M.Kontsevich's paper about deformation quantization https://arxiv.org/pdf/q-alg/9709040.pdf. Page3. He defines formal Poisson structure as the set of equivalence classes of Poisson structures depending formally on $\hbar$ : $$ \alpha=\alpha(\hbar)=\alpha_1 \hbar+\alpha_2 \hbar^2+\ldots \in \Gamma\left(X, \wedge^2 T_X\right)[[\hbar]], \quad[\alpha, \alpha]=0 \in \Gamma\left(X, \wedge^3 T_X\right)[[\hbar]] $$ modulo the action of the group of formal paths in the diffeomorphism group of $X$, starting at the identity diffeomorphism.
What is a formal path in the diffeomorphism group? In non-formal case I think it's just one parameter group of diffeomorphism, and the action here is the push-forward action of diffeomorphisms. My thought: Formal path locally can be seen as a series $\sum \hbar^i\phi_i$ where $\phi_i$ are diffeomorphisms, and $\phi_0=id$, like a Taylor expansion in the Lie group of diffeomorphsms of $M$, but then a point on a formal path may not lie in the group of diffeomorhisms since the series may not converge, the path goes out of the space...
So what does the formal path mean here?