Resources to learn second quantization formalism and how to implement it in code for quantum/computational chemistry research I want to know what are some useful and practical resources to learn the formalism of second quantization as it pertains to fermions to be used in solving Quantum Chemistry problems. I am particularly asking for resources that go beyond the symbolic formalism and have guides/examples on how to implement the second quantization ideas in code (regardless of comp. language).
The pink book: Molecular Electronic-Structure Theory from Helgaker is a good start on the topic with all the formalism but I am looking for other resources with coding examples or practical implemmentations?
You could check out any code set that implements configuration interaction wave function methods.  The Journal of Chemical Physics published an open-access article reviewing the state of ab-initio software, and it lists code sets that use CI.
 https://aip.scitation.org/doi/pdf/10.1063/5.0023185
Notably, NWChem uses the second quantization approach and is described in this open resource paper:  https://arxiv.org/pdf/1904.01131.pdf
Finding algorithms to rapidly create valid CI expansions was a big research area in the late 1970's, and the Graphical Unitary Group Approach was created.  There are several open source packages that use the GUGA, including GAMESS. https://www.msg.chem.iastate.edu/gamess/download.html   You can get GAMESS by requesting access and registering.  You could then review the implementation assuming a basic knowledge of FORTRAN.