class Error(Exception):
    def __init__(self, value=""):
        if not hasattr(self, "value"):
            self.value = value

    def __str__(self):
        return repr(self.value)


class InvalidSma(Error):
    message = "Invalid SMA period."


class ResourceNotFound(Error):
    message = "Resource not found."


class DateFormatError(Error):
    message = "Error with date parameters."


class Messages:
    INTERNAL_SERVER_ERROR = "Server error. please try again later."