class NodeConnectionFailure(Exception):
    ...


class ConnectionRequiresPortFailure(NodeConnectionFailure):
    'A port is required'
    ...


class ConnectionSelfFailure(NodeConnectionFailure):
    'Cannot connect a node to itself'
    ...


class ConnectionPointFailure(NodeConnectionFailure):
    'Connection point is not on top of the node port'
    ...


class ConnectionPortNotEmptyFailure(NodeConnectionFailure):
    'Port should be empty'
    ...


class ConnectionCycleFailure(NodeConnectionFailure):
    'Connection would introduce a cycle in the graph'
    ...


class ConnectionDataTypeFailure(NodeConnectionFailure):
    'Ports do not have compatible data types'
    ...


class PortsOfSameTypeError(NodeConnectionFailure):
    ...


class PortsAlreadyConnectedError(NodeConnectionFailure):
    ...


class MultipleInputConnectionError(NodeConnectionFailure):
    ...