Given the keyword string, parse a dictionary of options.

def extract_keywords(cls, line, items):
        """
        Given the keyword string, parse a dictionary of options.
        """
        unprocessed = list(reversed(line.split('=')))
        while unprocessed:
            chunk = unprocessed.pop()
            key = None
            if chunk.strip() in cls.allowed:
                key = chunk.strip()
            else:
                raise SyntaxError("Invalid keyword: %s" % chunk.strip())
            # The next chunk may end in a subsequent keyword
            value = unprocessed.pop().strip()
            if len(unprocessed) != 0:
                # Check if a new keyword has begun
                for option in cls.allowed:
                    if value.endswith(option):
                        value = value[:-len(option)].strip()
                        unprocessed.append(option)
                        break
                else:
                    raise SyntaxError("Invalid keyword: %s" % value.split()[-1])
            keyword = '%s=%s' % (key, value)
            try:
                items.update(eval('dict(%s)' % keyword))
            except:
                raise SyntaxError("Could not evaluate keyword: %s" % keyword)
        return items