def extract_label_signature(autodoc_line):
    """Extract the object name and signature of the object being document.

    For example::

        >>> extract_label_signature(':: foo(a, b)')
        'foo', 'foo(a, b)'
        >>> extract_label_signature(':: foo')
        'foo', None
    """
    _, what = autodoc_line.split('::')
    if '(' in what:
        signature = what.strip()
        what, *_ = what.partition('(')
    else:
        signature = None
    return what.strip(), signature
