How to use the pandocfilters.sys.stdin.read function in pandocfilters

def main():
    # This grabs the output of `pandoc` as json file, retrieves `metadata` to
    # check for draft status, and runs the document through `handle_comments`.
    # Then adds any needed entries to `metadata` and passes the output back out
    # to `pandoc`. This code is modeled after
    # .
    global DRAFT
    document = json.loads(sys.stdin.read())
    if len(sys.argv) > 1:
        format = sys.argv[1]
    else:
        format = ''

    if 'meta' in document:           # new API
        metadata = document['meta']
    elif document[0]:                # old API
        metadata = document[0]['unMeta']

    if 'draft' in metadata:
        DRAFT = metadata['draft']['c']
    else:
        DRAFT = False

    newDocument = document

def main():
    doc = pf.json.loads(pf.sys.stdin.read())
    if len(pf.sys.argv) > 1:
        format = pf.sys.argv[1]
    else:
        format = ""

    metadata = doc[0]['unMeta']
    args = {k: v['c'] for k, v in metadata.items()}
    autoref = args.get('autoref', True)

    refmanager = ReferenceManager(autoref=autoref)

    altered = doc
    for action in refmanager.reference_filter:
        altered = pf.walk(altered, action, format, metadata)

    pf.json.dump(altered, pf.sys.stdout)

to stdout.

    The argument is a function action(key, value, format, meta),
    where key is the type of the pandoc object (e.g. 'Str', 'Para'),
    value is the contents of the object (e.g. a string for 'Str',
    a list of inline elements for 'Para'), format is the target
    output format (which will be taken for the first command line
    argument if present), and meta is the document's metadata.

    If the function returns None, the object to which it applies
    will remain unchanged.  If it returns an object, the object will
    be replaced.  If it returns a list, the list will be spliced in to
    the list to which the target object belongs.  (So, returning an
    empty list deletes the object.)
    """
    doc = pf.json.loads(pf.sys.stdin.read())
    if len(pf.sys.argv) > 1:
        format = pf.sys.argv[1]
    else:
        format = ""

    if type(actions) is type(toJSONFilter):
        altered = pf.walk(doc, actions, format, doc[0]['unMeta'])
    elif type(actions) is list:
        altered = doc
        for action in actions:
            altered = pf.walk(altered, action, format, doc[0]['unMeta'])

    pf.json.dump(altered, pf.sys.stdout)

to stdout.

    The argument is a function action(key, value, format, meta),
    where key is the type of the pandoc object (e.g. 'Str', 'Para'),
    value is the contents of the object (e.g. a string for 'Str',
    a list of inline elements for 'Para'), format is the target
    output format (which will be taken for the first command line
    argument if present), and meta is the document's metadata.

    If the function returns None, the object to which it applies
    will remain unchanged.  If it returns an object, the object will
    be replaced.  If it returns a list, the list will be spliced in to
    the list to which the target object belongs.  (So, returning an
    empty list deletes the object.)
    """
    doc = pf.json.loads(pf.sys.stdin.read())
    if len(pf.sys.argv) > 1:
        format = pf.sys.argv[1]
    else:
        format = ""

    if type(actions) is type(toJSONFilter):
        altered = pf.walk(doc, actions, format, doc[0]['unMeta'])
    elif type(actions) is list:
        altered = doc
        for action in actions:
            altered = pf.walk(altered, action, format, doc[0]['unMeta'])

    pf.json.dump(altered, pf.sys.stdout)