my_demo_module.py

class DummyClass:
    """Class to print input text

    Attributes:
    ------------
    text : string
    """
    
    def __init__(self, text):
        self.text = text

    def check(self):
        """ Checks if input is string and non-empty

        Returns
        -------
        True if input is string and non-empty
        Raises error otherwise
        """
        
        # check if input is a string
        if not isinstance(self.text, str):
            raise TypeError("Expected a string")
        # check if input is non-empty
        elif len(self.text) <= 0:
            raise ValueError("Expected a non-empty string")
        return True

    def print_text(self):
        """prints input text in lower case
        
        Returns
        -------
        None
        """
        
        if self.check():
            # convert string to lower case
            self._text_lower()
            self.text = "*****************\n"+self.text+"\n*****************\n"
            print(self.text)

    def _text_lower(self):
        """to convert text to lower case

        Returns
        -------
        None

        """
        self.text = self.text.lower()