Added approximate interface boundary for consumer producer pattern.

Concrete implementations can leverage any tool, in this case being queue and pubsub/streams.

interface.py

@@ -0,0 +1,39 @@
+import abc
+from typing import Protocol, Optional, TypeVar
+
+
+t_consumer_id = TypeVar('consumer_id', bound=str)
+
+
+class Consumer(Protocol):
+  """This class consumes input.
+  Each consumer entry creates a dedicated channel to consume into.
+  """
+
+  @abc.abstractmethod
+  def setup(self, channel: Optional[str] = None, **kwargs) -> t_consumer_id:
+    """Setup the consumer."""
+    raise NotImplementedError
+
+  @abc.abstractmethod
+  def consume(self, data: dict, **optional_attrs) -> None:
+    """Consume input."""
+    raises NotImplementedError
+
+
+class Producer(Protocol):
+  """This class produces output.
+  
+  Each producer entry publishes from a dedicated channel.
+  """
+
+  @abc.abstractmethod
+  def setup(self, consumer_id: t_consumer_id, **kwargs) -> None:
+    """Setup the producer."""
+    raise NotImplementedError
+
+  @abc.abstractmethod
+  def get(self, **optional_attrs) -> None:
+    """Returns output."""
+    raise NotImplementedError
+