import re


def get_docstring_option_help(obj, arg):
    """Return the docstring help from an argument of a given object

    Parameters
    ----------
        obj : `class`, required
            `class` of the object from which to read the docstring
        arg : string, required
            name of the argument from which to read the docstring help
    
    Returns
    -------
        string : the docstring help
    """
    doc_as_list = obj.__init__.__doc__.split("\n")
    for i in range(len(doc_as_list)):
        if re.search(".*?" + arg + " : .*?", doc_as_list[i]):
            return doc_as_list[i+1]
    else:
        raise RuntimeError("Unable to find arg {} from generated docstring of {}".format(arg, type(obj)))