"""File containing base class for local black box explainers

    Attributes:
        ABC: Ensure compatibility of Abstract Base Class with Python versions

"""

import abc
import sys

# Ensure compatibility with Python 2/3
if sys.version_info >= (3, 4):
    ABC = abc.ABC
else:
    ABC = abc.ABCMeta(str('ABC'), (), {})


class LocalBBExplainer(ABC):

    """
    LocalBBExplainer is the base class for local post-hoc black-box explainers (LBBE).
    Such explainers are model agnostic and generally require access to model's predict function alone.
    Examples include LIME[#1]_, SHAP[#2]_, etc..

    References:
        .. [#1] “Why Should I Trust You?” Explaining the Predictions of Any Classifier, ACM SIGKDD 2016.
        Marco Tulio Ribeiro, Sameer Singh, Carlos Guestrin. https://arxiv.org/abs/1602.04938.
        .. [#2] A Unified Approach to Interpreting Model Predictions, NIPS 2017.
        Lundberg, Scott M and Lee, Su-In. https://arxiv.org/abs/1705.07874

    """

    def __init__(self, *argv, **kwargs):

        """
        Initialize a LocalBBExplainer object.
        """

    def set_params(self, *argv, **kwargs):
        """
        Set parameters for the explainer.
        """
        raise NotImplementedError

    @abc.abstractmethod
    def explain_instance(self, *argv, **kwargs):
        """
        Explain an input instance x.
        """
        raise NotImplementedError
