TEQUILA is a fixed-boundary equilibrium solver that uses cubic-Hermite finite elements in the radial direction, Fourier modes in the poloidal angle, and a Miller extended harmonic (MXH) flux-surface parametrization [Arbon 2021]. MXH provides an efficient representation of flux surfaces.
The high-level implementation borrows extensively: Jardin, Stephen. Computational Methods in Plasma Physics. CRC Press, 2010.
TEQUILA uses COCOS 11 convention.
For more details, see the online documentation.