def _get_image_number(image_file_name: str) -> int:
    """Get the number of the image file with a particular pattern at a particular site.

    Args:
        image_file_name (str): Name of the file

    Examples:
        >>> _get_image_number('Ni Patterns 0 Deformation Specimen 1 Speed2 Map Data 2_0001.tiff')
        1
        >>> _get_image_number('Ni Patterns 0 Deformation Specimen 1 Speed2 Map Data 2_0100.tiff')
        100

    Returns:
        (int) The number of the image (related to a pattern's ID) in the filename.

    """
    return int(str(image_file_name).rsplit('_', 1)[1].split('.', 1)[0])