'Updates the dictionary with a single header line.
>>> h = HTTPHeaders()
>>> h.parse_line("Content-Type: text/html")
>>> h.get(\'content-type\')
\'text/html\''

def parse_line(self, line):

    if line[0].isspace():
        new_part = ('    ' + line.lstrip())
        self._as_list[self._last_key][(-1)] += new_part
        dict.__setitem__(self, self._last_key, (self[self._last_key] + new_part))
    else:
        (name, value) = line.split(':', 1)
        self.add(name, value.strip())
