Reads an input image `fname` and returns the decoded raw bytes.
        Examples
        --------
        >>> dataIter.read_image('Face.jpg') # returns decoded raw bytes.

def read_image(self, fname):
        """Reads an input image `fname` and returns the decoded raw bytes.
        Examples
        --------
        >>> dataIter.read_image('Face.jpg') # returns decoded raw bytes.
        """
        with open(os.path.join(self.path_root, fname), 'rb') as fin:
            img = fin.read()
        return img