Error Model For Sequence Simulation

Question

[dli]

Is there a simple example for the error mode while simulating next generation sequencing reads? i know that wgsim in samtools and many other tools such as simNGS can do reads simulation, however, i can not understand them when reading their code...what i want would be step by step explanation of how to using a error model such as substitution, insertion or deletion etc to generate mutated and simulated reads? If there is a code implementation in C or Python would be better. Thanks.