# Concentration -- optional argument used to specify the concentration

## Description

In this package, each complex $C$ has a concentration $(\ell, h)$ such that $\ell \leq h$. For all $i < \ell$ and all $i > h$, the term $C_i$ is zero. When $\ell \leq i \leq h$, the module $C_i$ may or may not be zero.

Several methods use this optional argument to specify the concentration of their outputs.