import re


def parse_attributes_block_classes(block):
    """Return the classes in `block`.

    Parameters
    ==========
    block : string
        Block to search in

    Returns
    =======
    classes : list of strings (empty if none found)

    """
    pattern = re.compile(r'[.]\w+\b')
    s = pattern.findall(block)
    s = [c[1:] for c in s]
    return s