Example of making an interface in Python.

trainable.py

# Copyright 2016 The TensorFlow Authors. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
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# ==============================================================================

"""`Trainable` interface."""

from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

import abc


class Trainable(object):
  """Interface for objects that are trainable by, e.g., `Experiment`.
  """
  __metaclass__ = abc.ABCMeta

  @abc.abstractmethod
  def fit(self, x=None, y=None, input_fn=None, steps=None, batch_size=None,
          monitors=None, max_steps=None):
    """Trains a model given training data `x` predictions and `y` labels.

    Args:
      x: Matrix of shape [n_samples, n_features...]. Can be iterator that
         returns arrays of features. The training input samples for fitting the
         model. If set, `input_fn` must be `None`.
      y: Vector or matrix [n_samples] or [n_samples, n_outputs]. Can be
         iterator that returns array of labels. The training label values
         (class labels in classification, real numbers in regression). If set,
         `input_fn` must be `None`.
      input_fn: Input function returning a tuple of:
          features - Dictionary of string feature name to `Tensor` or `Tensor`.
          labels - `Tensor` or dictionary of `Tensor` with labels.
        If input_fn is set, `x`, `y`, and `batch_size` must be `None`.
      steps: Number of steps for which to train model. If `None`, train forever.
        'steps' works incrementally. If you call two times fit(steps=10) then
        training occurs in total 20 steps. If you don't want to have incremental
        behaviour please set `max_steps` instead. If set, `max_steps` must be
        `None`.
      batch_size: minibatch size to use on the input, defaults to first
        dimension of `x`. Must be `None` if `input_fn` is provided.
      monitors: List of `BaseMonitor` subclass instances. Used for callbacks
        inside the training loop.
      max_steps: Number of total steps for which to train model. If `None`,
        train forever. If set, `steps` must be `None`.

        Two calls to `fit(steps=100)` means 200 training
        iterations. On the other hand, two calls to `fit(max_steps=100)` means
        that the second call will not do any iteration since first call did
        all 100 steps.

    Returns:
      `self`, for chaining.
    """
    raise NotImplementedError