A diagram showing the structure of a wrapper is given in Figure . Currently, there are built-in wrappers for Psi4 and ORCA, which act as examples for how further wrappers could be written. The principle idea is that there are a list of possible methods, and these are marked as 'available' to the API when implemented in a particular wrapper. The calculation is then called via the run command, with only a molecule and the name of the method -e.g. 'ccsd', for coupled cluster with single and double excitations. The result is then returned in a native Python data type.