'Return the description to be used for this argument
@return: C{str}'

def getDescription(self, longname):

    if (longname in self.descriptions):
        return self.descriptions[longname]
    try:
        descr = self.flagNameToDefinition[longname][1]
    except KeyError:
        try:
            descr = self.paramNameToDefinition[longname][2]
        except KeyError:
            descr = None
    if (descr is not None):
        return descr
    longMangled = longname.replace('-', '_')
    obj = getattr(self.options, ('opt_%s' % longMangled), None)
    if (obj is not None):
        descr = descrFromDoc(obj)
        if (descr is not None):
            return descr
    return longname
