Return a multidigit int or float number.

def number(self):
        """Return a multidigit int or float number."""
        number = ''
        while self.char is not None and self.char.isdigit():
            number += self.char
            self.advance()

        if self.char == '.':
            number += self.char
            self.advance()

            while self.char is not None and self.char.isdigit():
                number += self.char
                self.advance()

            token = Token(Nature.FLOAT_NUMBER, number)

        else:
            token = Token(Nature.INT_NUMBER, number)

        return token