Composite basis set

Hi,
I am having hard times with the definition of a ‘composite’ basis set within the PyAPI. In other words, in psi4 is possible to mix the basis sets simply
basis {
assign DZ
assign C 3-21G
assign H1 sto-3g
assign C1 sto-3g
}
What is the equivalent syntax in the case of the Psi4 PyAPI? Alternatively, would it be possible to use psi4.core.BasisSet.build() to achieve this goal?
Thanks in advance
M

Solved in
Custom defined basis set