'@param tokenSource A TokenSource instance (usually a Lexer) to pull
the tokens from.
@param channel Skip tokens on any channel but this one; this is how we
skip whitespace...'

def __init__(self, tokenSource=None, channel=DEFAULT_CHANNEL):

    TokenStream.__init__(self)
    self.tokenSource = tokenSource
    self.tokens = []
    self.channelOverrideMap = {}
    self.discardSet = set()
    self.channel = channel
    self.discardOffChannelTokens = False
    self.p = (-1)
    self.lastMarker = None
