pdl: Fix docstring which promises too much

        return get_packet_ancestor(decl.file.packet_scope[decl.parent_id])

def get_derived_packets(decl: Union[PacketDeclaration, StructDeclaration]

def get_derived_packets(

    decl: Union[PacketDeclaration, StructDeclaration]

) -> List[Tuple[List[Constraint], Union[PacketDeclaration, StructDeclaration]]]:

    """Return the list of packets or structs that immediately derive from the

    selected packet or struct, coupled with the field constraints.

def is_bit_field(field: Field) -> bool:

    """Identify fields that can have bit granularity.

    These include: ScalarField, FixedField, TypedefField with enum type,

    SizeField, and CountField. Returns the size of the field in bits."""

    SizeField, and CountField."""

    if isinstance(field, (ScalarField, SizeField, CountField, FixedField, ReservedField)):

        return True