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"""A class for Abstract Configuration interface."""
import abc
from typing import Any, Union

# Python 2 and 3 compatible Abstract class
ABC = abc.ABCMeta('ABC', (object,), {})


class ConfigInterface(ABC):
    """
    Config Interface
    """
    @abc.abstractmethod
    def to_json(self) -> dict:
        """
        Convert the config object to json formatted dict.

        Returns:
            dict: json formatted dict of the config object.
        """
        raise NotImplementedError('The subclass of ConfigInterface must implement this method')

    @abc.abstractmethod
    def copy(self) -> Any:
        """
        Copy the config object.

        Returns:
            Any: a copy of the config object.
        """
        raise NotImplementedError('The subclass of ConfigInterface must implement this method')

    @staticmethod
    @abc.abstractmethod
    def from_json(json_obj: Union[dict, str]) -> Any:
        """
        Create the config object from json in either string or dict format.

        Args:
            json_obj (Union[dict, str]): json in either string or dict format.

        Returns:
            Any: the config object.
        """
        raise NotImplementedError('The subclass of ConfigInterface must implement this method')