import json


def isjson(value):
    """
    Return whether or not given value is valid JSON.
    If the value is valid JSON, this function returns ``True``, otherwise ``False``.

    Examples::

        >>> isjson('{"Key": {"Key": {"Key": 123}}}')
        True

        >>> isjson('{ key: "value" }')
        False

    :param value: string to validate JSON
    """
    try:
        decoded_json = json.loads(value)
    except ValueError:
        return False
    return True