'Determine if the file is in RNA dot plot format.'

def sniff(self, filename):

    if check_image_type(filename, ['EPS']):
        seq = False
        coor = False
        pairs = False
        with open(filename) as handle:
            for line in handle:
                line = line.strip()
                if line:
                    if line.startswith('/sequence'):
                        seq = True
                    elif line.startswith('/coor'):
                        coor = True
                    elif line.startswith('/pairs'):
                        pairs = True
                if (seq and coor and pairs):
                    return True
    return False
