class_docstr: Subclass of Function that allows multiple functions and variables to
  be defined in a single code string. The code must contain a main() function
  definition.
class_docstr_tok: ["Subclass","of","Function","that","allows","multiple","functions","and","variables","to","be","defined","in","a","single","code","string",".","The","code","must","contain","a","main","(",")","function","definition","."]
docstr: Create a new ChainFunction and attach to $var.
docstr_tok: ["Create","a","new","ChainFunction","and","attach","to","$","var","."]
code: def add_chain(self, var):
      """Create a new ChainFunction and attach to $var."""
      chain = FunctionChain(var, [])
      self._chains[var] = chain
      self[var] = chain
  
imports: from collections import OrderedDict
  import logging
  import re
  import numpy
  from ...util.eq import eq
  from ...util import logger
  from .None import parsing
  from .shader_object import ShaderObject
  from .variable import Variable, Varying
  from .expression import TextExpression, FunctionCall
label_desc: Use image node_id 6 for calling the MainFunction obj's underlying member method code with example usage: obj.add_chain(var) without return types