  The two-dimensional kagome lattice hosts Dirac fermions at its Brillouin zone
corners K and K', analogous to the honeycomb lattice. In the density functional
theory electronic structure of ferromagnetic kagome metal Fe$_3$Sn$_2$, without
spin-orbit coupling we identify two energetically split helical nodal lines
winding along $z$ in the vicinity of K and K' resulting from the trigonal
stacking of the kagome layers. We find that hopping across A-A stacking
introduces a layer splitting in energy while that across A-B stacking controls
the momentum space amplitude of the helical nodal lines. The effect of
spin-orbit coupling is found to resemble that of a Kane-Mele term, where the
nodal lines can either be fully gapped to quasi-two-dimensional massive Dirac
fermions, or remain gapless at discrete Weyl points depending on the
ferromagnetic moment orientation. Aside from numerically establishing
Fe$_3$Sn$_2$ as a model Dirac kagome metal, our results provide insights into
materials design of topological phases from the lattice point of view, where
paradigmatic low dimensional lattice models often find realizations in
crystalline materials with three-dimensional stacking.
