human
Here's a good function header given the following:
I wrote the below code

    base_path = os.path.abspath(os.path.dirname(relative_to))
    (name_suffix, target_dir) = _create_module_dir(base_path, name)
    if (not package):
        cffi_wrapper_name = ('_' + name_suffix)
    else:
        cffi_wrapper_name = (name.rpartition('.')[0] + '.{0}._{0}'.format(name_suffix))
    (wrapper_source, include_dirs) = _setup_wrapper(with_cuda)
    include_dirs.extend(kwargs.pop('include_dirs', []))
    if isinstance(headers, str):
        headers = [headers]
    all_headers_source = ''
    for header in headers:
        with open(os.path.join(base_path, header), 'r') as f:
            all_headers_source += (f.read() + '\n\n')
    ffi = cffi.FFI()
    sources = [os.path.join(base_path, src) for src in sources]
    ffi.set_source(cffi_wrapper_name, (wrapper_source + all_headers_source), sources=sources, include_dirs=include_dirs, **kwargs)
    ffi.cdef((_typedefs + all_headers_source))
    _make_python_wrapper(name_suffix, ('_' + name_suffix), target_dir)
    def build():
        _build_extension(ffi, cffi_wrapper_name, target_dir, verbose)
    ffi.build = build
    return ffi

What's a good function header?
assistant
#Here's a good function header.

def create_extension(name, headers, sources, verbose=True, with_cuda=False, package=False, relative_to='.', **kwargs):