class_docstr: Convert mathematical symbols such as \<longrightarrow> in Isabelle
  or \longrightarrow in LaTeX into Unicode characters.
  
  This is mostly useful for HTML or console output when you want to
  approximate the source rendering you'd see in an IDE.
  
  Options accepted:
  
  `lang` : string
     The symbol language. Must be one of ``'isabelle'`` or
     ``'latex'``.  The default is ``'isabelle'``.
class_docstr_tok: ["Convert","mathematical","symbols","such","as","\\","<","longrightarrow",">","in","Isabelle","or","\\longrightarrow","in","LaTeX","into","Unicode","characters",".","This","is","mostly","useful","for","HTML","or","console","output","when","you","want","to","approximate","the","source","rendering","you","'d","see","in","an","IDE",".","Options","accepted",":","`","lang","`",":","string","The","symbol","language",".","Must","be","one","of","``","'isabelle","'","``","or","``","'latex","'","``",".","The","default","is","``","'isabelle","'","``","."]
code: def filter(self, lexer, stream):
      for ttype, value in stream:
          if value in self.symbols:
              yield ttype, self.symbols[value]
          else:
              yield ttype, value
  
imports: import re
  from pygments.token import String, Comment, Keyword, Name, Error, Whitespace, string_to_tokentype
  from pygments.filter import Filter
  from pygments.util import get_list_opt, get_int_opt, get_bool_opt, get_choice_opt, ClassNotFound, OptionError
  from pygments.plugin import find_plugin_filters
label_desc: Use image node_id 2 for calling the SymbolFilter obj's underlying member method code with example usage: obj.filter(lexer, stream) without return types