How to use the gaphor.diagram.connectors.IConnect.register function in gaphor

otc = self.get_connected(opposite)
        if opposite and isinstance(otc, (ForkNodeItem, DecisionNodeItem)):
            adapter = IConnect(otc, line)
            adapter.combine_nodes()

    def disconnect_subject(self, handle):
        super().disconnect_subject(handle)
        line = self.line
        opposite = line.opposite(handle)
        otc = self.get_connected(opposite)
        if opposite and isinstance(otc, (ForkNodeItem, DecisionNodeItem)):
            adapter = IConnect(otc, line)
            adapter.decombine_nodes()


IConnect.register(ActionItem, FlowItem)(FlowConnect)
IConnect.register(ActivityNodeItem, FlowItem)(FlowConnect)
IConnect.register(ObjectNodeItem, FlowItem)(FlowConnect)
IConnect.register(SendSignalActionItem, FlowItem)(FlowConnect)
IConnect.register(AcceptEventActionItem, FlowItem)(FlowConnect)


class FlowForkDecisionNodeConnect(FlowConnect):
    """
    Abstract class with common behaviour for Fork/Join node and
    Decision/Merge node.
    """

    element: Union[ForkNodeItem, DecisionNodeItem]
    fork_node_cls: Type[UML.ControlNode]
    join_node_cls: Type[UML.ControlNode]

def disconnect(self, handle):
        c1 = self.get_connected(handle)
        opposite = self.line.opposite(handle)
        c2 = self.get_connected(opposite)
        if c1 and c2:
            if (
                isinstance(c1.subject, UML.Comment)
                and c2.subject in c1.subject.annotatedElement
            ):
                del c1.subject.annotatedElement[c2.subject]
            elif c2.subject and c1.subject in c2.subject.annotatedElement:
                del c2.subject.annotatedElement[c1.subject]
        super().disconnect(handle)


@IConnect.register(CommentLineItem, LinePresentation)
class InverseCommentLineLineConnect(CommentLineLineConnect):
    """
    In case a line is disconnected that contains a comment-line,
    the comment line unlinking should happen in a correct way.
    """

    def __init__(self, line, element):
        super().__init__(element, line)

"""
Use cases related connection adapters.
"""

from gaphor import UML
from gaphor.diagram.usecases.usecase import UseCaseItem
from gaphor.diagram.usecases.extend import ExtendItem
from gaphor.diagram.usecases.include import IncludeItem
from gaphor.diagram.connectors import IConnect, RelationshipConnect


@IConnect.register(UseCaseItem, IncludeItem)
class IncludeConnect(RelationshipConnect):
    """Connect use cases with an include item relationship."""

    def allow(self, handle, port):
        line = self.line
        element = self.element

        if not (element.subject and isinstance(element.subject, UML.UseCase)):
            return None

        return super().allow(handle, port)

    def reconnect(self, handle, port):
        self.reconnect_relationship(
            handle, UML.Include.addition, UML.Include.includingCase
        )

subject = element.subject

        # Check if no other items are connected
        connections = self.canvas.get_connections(connected=element)
        connected_items = [
            c
            for c in connections
            if isinstance(c.item, TransitionItem) and c.item is not line
        ]
        if handle is line.head and not any(connected_items):
            return super().allow(handle, port)
        else:
            return None


@IConnect.register(HistoryPseudostateItem, TransitionItem)
class HistoryPseudostateTransitionConnect(VertexConnect):
    """Connect history pseudostate using transition item.

    It modifies InitialPseudostateItem._connected attribute to disallow
    connection of more than one transition.
    """

    def allow(self, handle, port):
        """
        """
        return super().allow(handle, port)

line = self.line
        subject = self.element.subject

        is_final = isinstance(subject, UML.FinalState)
        if (
            isinstance(subject, UML.State)
            and not is_final
            or handle is line.tail
            and is_final
        ):
            return super().allow(handle, port)
        else:
            return None


@IConnect.register(InitialPseudostateItem, TransitionItem)
class InitialPseudostateTransitionConnect(VertexConnect):
    """Connect initial pseudostate using transition item.

    It modifies InitialPseudostateItem._connected attribute to disallow
    connection of more than one transition.
    """

    def allow(self, handle, port):
        """
        Glue to initial pseudostate with transition's head and when there are
        no transitions connected.
        """
        assert self.canvas

        line = self.line
        element = self.element

adapter = IConnect(otc, line)
            adapter.combine_nodes()

    def disconnect_subject(self, handle):
        super().disconnect_subject(handle)
        line = self.line
        opposite = line.opposite(handle)
        otc = self.get_connected(opposite)
        if opposite and isinstance(otc, (ForkNodeItem, DecisionNodeItem)):
            adapter = IConnect(otc, line)
            adapter.decombine_nodes()


IConnect.register(ActionItem, FlowItem)(FlowConnect)
IConnect.register(ActivityNodeItem, FlowItem)(FlowConnect)
IConnect.register(ObjectNodeItem, FlowItem)(FlowConnect)
IConnect.register(SendSignalActionItem, FlowItem)(FlowConnect)
IConnect.register(AcceptEventActionItem, FlowItem)(FlowConnect)


class FlowForkDecisionNodeConnect(FlowConnect):
    """
    Abstract class with common behaviour for Fork/Join node and
    Decision/Merge node.
    """

    element: Union[ForkNodeItem, DecisionNodeItem]
    fork_node_cls: Type[UML.ControlNode]
    join_node_cls: Type[UML.ControlNode]

    def allow(self, handle, port):
        # No cyclic connect is possible on a Flow/Decision node:

from gaphor import UML
from gaphor.diagram.presentation import Classified
from gaphor.diagram.profiles.extension import ExtensionItem
from gaphor.diagram.connectors import IConnect, RelationshipConnect


@IConnect.register(Classified, ExtensionItem)
class ExtensionConnect(RelationshipConnect):
    """Connect class and stereotype items using an extension item."""

    line: ExtensionItem

    def allow(self, handle, port):
        line = self.line
        subject = self.element.subject

        if handle is line.head:
            # Element at the head should be a class
            # (implies stereotype as well)
            allow = isinstance(subject, UML.Class)
        elif handle is line.tail:
            # Element at the tail should be a stereotype
            allow = isinstance(subject, UML.Stereotype)

Interface item related connections.

The connectors implemented in this module check if connection is possible
to folded interface, see `gaphor.diagram.classes.interface` documentation
for details.
"""


from gaphor.diagram.classes.classconnect import DependencyConnect, ImplementationConnect
from gaphor.diagram.classes.dependency import DependencyItem
from gaphor.diagram.classes.implementation import ImplementationItem
from gaphor.diagram.classes.interface import Folded, InterfaceItem
from gaphor.diagram.connectors import IConnect


@IConnect.register(InterfaceItem, ImplementationItem)
class ImplementationInterfaceConnect(ImplementationConnect):
    """Connect interface item and a behaviored classifier using an
    implementation.
    """

    def connect(self, handle, port):
        """
        Implementation item can be changed to draw in solid mode, when
        connected to folded interface.
        """
        super().connect(handle, port)
        if handle is self.line.head:
            self.line.request_update()

    def disconnect(self, handle):
        """

def disconnect_subject(self, handle):
        super().disconnect_subject(handle)
        line = self.line
        opposite = line.opposite(handle)
        otc = self.get_connected(opposite)
        if opposite and isinstance(otc, (ForkNodeItem, DecisionNodeItem)):
            adapter = IConnect(otc, line)
            adapter.decombine_nodes()


IConnect.register(ActionItem, FlowItem)(FlowConnect)
IConnect.register(ActivityNodeItem, FlowItem)(FlowConnect)
IConnect.register(ObjectNodeItem, FlowItem)(FlowConnect)
IConnect.register(SendSignalActionItem, FlowItem)(FlowConnect)
IConnect.register(AcceptEventActionItem, FlowItem)(FlowConnect)


class FlowForkDecisionNodeConnect(FlowConnect):
    """
    Abstract class with common behaviour for Fork/Join node and
    Decision/Merge node.
    """

    element: Union[ForkNodeItem, DecisionNodeItem]
    fork_node_cls: Type[UML.ControlNode]
    join_node_cls: Type[UML.ControlNode]

    def allow(self, handle, port):
        # No cyclic connect is possible on a Flow/Decision node:
        head, tail = self.line.head, self.line.tail
        subject = self.element.subject