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"""Interfaces related to streams of values or objects."""

import abc

import six

class Consumer(six.with_metaclass(abc.ABCMeta)):
  """Interface for consumers of finite streams of values or objects."""

  @abc.abstractmethod
  def consume(self, value):
    """Accepts a value.

    Args:
      value: Any value accepted by this Consumer.
    """
    raise NotImplementedError()

  @abc.abstractmethod
  def terminate(self):
    """Indicates to this Consumer that no more values will be supplied."""
    raise NotImplementedError()

  @abc.abstractmethod
  def consume_and_terminate(self, value):
    """Supplies a value and signals that no more values will be supplied.

    Args:
      value: Any value accepted by this Consumer.
    """
    raise NotImplementedError()