$ gemmi fprime -h
Usage:
 gemmi fprime [options] ELEMENT[...]
Prints anomalous scattering factors f' and f".

Options:
  -h, --help               Print usage and exit.
  -V, --version            Print version and exit.
  -e, --energy=ENERGY      Energy [eV]
  -w, --wavelength=LAMBDA  Wavelength [A]