When subclassing remember to call SubtitleChangeCommand::setup() to perform generic
        checks.

def setup(self):
        """When subclassing remember to call SubtitleChangeCommand::setup() to perform generic
        checks."""
        if not isinstance(self.filePath, str):
            raise TypeError("File path is not a string!")
        if self.controller is None:
            raise ValueError("Command controller hasn't been specified!")