- Usage:
`HH^i f`

- Function: cohomology
- Inputs:
`i`, an integer`f`, a chain complex map

- Optional inputs:
`Degree => ...`(missing documentation),

- Outputs:
- a matrix, the
`i`-th cohomology map induced by the chain complex map`f`

- a matrix, the

The command provides the map on the `i`-th cohomology module induced by a map `f` of chain complexes.

- cohomology -- general cohomology functor
- HH -- general homology and cohomology functor
- ChainComplex -- the class of all chain complexes