class InformalParserInterface:
    def load_data_source(self, path: str, file_name: str) -> str:
        """Load in the file for extracting text."""
        pass

    def extract_text(self, full_file_name: str) -> dict:
        """Extract text from the currently loaded file."""
        pass

class PdfParser(InformalParserInterface):
    """Extract text from a PDF"""
    def load_data_source(self, path: str, file_name: str) -> str:
        """Overrides InformalParserInterface.load_data_source()"""
        pass

    def extract_text(self, full_file_path: str) -> dict:
        """Overrides InformalParserInterface.extract_text()"""
        pass

class EmlParser(InformalParserInterface):
    """Extract text from an email"""
    def load_data_source(self, path: str, file_name: str) -> str:
        """Overrides InformalParserInterface.load_data_source()"""
        pass

    def extract_text_from_email(self, full_file_path: str) -> dict:
        """A method defined only in EmlParser.
        Does not override InformalParserInterface.extract_text()
        """
        pass

print(issubclass(PdfParser,InformalParserInterface))
print(issubclass(EmlParser,InformalParserInterface))
