':param header_name: The name of the header we want the value for
:return: The value for a header given a name (be case insensitive)'

def iget(self, header_name, default=None):

    lower = string.lower
    lower_header_name = lower(header_name)
    for (stored_header_name, value) in self.iteritems():
        if (lower_header_name == lower(stored_header_name)):
            return (value, stored_header_name)
    return (default, None)
