Generates the chunks of lowdata from the list of modules

def _compile_state(sls_opts, mods=None):
    '''
    Generates the chunks of lowdata from the list of modules
    '''
    st_ = HighState(sls_opts)

    if not mods:
        return st_.compile_low_chunks()

    high_data, errors = st_.render_highstate({sls_opts['saltenv']: mods})
    high_data, ext_errors = st_.state.reconcile_extend(high_data)
    errors += ext_errors
    errors += st_.state.verify_high(high_data)
    if errors:
        return errors

    high_data, req_in_errors = st_.state.requisite_in(high_data)
    errors += req_in_errors
    high_data = st_.state.apply_exclude(high_data)
    # Verify that the high data is structurally sound
    if errors:
        return errors

    # Compile and verify the raw chunks
    return st_.state.compile_high_data(high_data)