import logging


def check_image_input(export_type):
    """ Function checks if file type is .jpg, .png or .tiff
   
    :param export_type: user identified file type for image to be saved as
    :raises ValueError: if file extension is not .jpg, .png or .tiff
    :returns True: if pass test
    """
    
    if export_type.lower().endswith('.jpg') or export_type.lower().endswith('.png') or export_type.lower().endswith('.tiff'):
        return True
    else:
        logging.info('incorrect export file extension')
        raise ValueError('File can only export as .jpg, .png, .tiff')