def portage_detect_single(atom, exec_fn = read_stdout ):

    std_out = exec_fn(['portageq', 'match', '/', atom])

    # TODO consdier checking the name of the package returned
    # Also, todo, figure out if just returning true if two packages are returned is cool..
    return len(std_out) >= 1
Iterates over the fields which are actually set.
dataset/ETHPy150Open ros-infrastructure/rosdep/src/rosdep2/platforms/gentoo.py/portage_detect_single--crossover with--dataset/ETHPy150Open google/grr/grr/lib/rdfvalues/structs.py/RDFStruct.ListSetFields