def push_source(self, newstream, newfile=None):
if isinstance(newstream, basestring):<EOL><INDENT>newstream = StringIO(newstream)<EOL><DEDENT>self.filestack.appendleft((self.infile, self.instream, self.lineno))<EOL>self.infile = newfile<EOL>self.instream = newstream<EOL>self.lineno = <NUM_LIT:1><EOL>
Push an input source onto the lexer's input source stack.