'Encode a L{list} of header values to a L{list} of UTF-8 encoded
bytestrings if required.
@param values: A list of HTTP header values.
@type values: L{list} of L{bytes} or L{unicode} (mixed types allowed)
@return: C{values}, with each item encoded if required
@rtype: L{list} of L{bytes}'

def _encodeValues(self, values):

    newValues = []
    for value in values:
        newValues.append(self._encodeValue(value))
    return newValues
