def getOCGList(pdf):
    """Return a list of Optional Content Groups in the given pdf as strings."""

def OCGRename(pdf, n_from, n_to):
    """Rename an optional content group."""

def OCGOrderAll(pdf):
    """Ensure that every optional content group appears in the OCG order list.
    """

def OCGCoalesce(pdf):
    """Coalesce optional content groups. For example, if we merge or stamp two
    files both with an OCG called "Layer 1", we will have two different
    optional content groups. This function will merge the two into a single
    optional content group."""
