docstr: Convert a list of ASTObjects into a JSON AST
docstr_tok: ["Convert","a","list","of","ASTObjects","into","a","JSON","AST"]
code: def to_json(self, validate=True) -> Dict[str, JSONVal]:
      """
      Convert a list of ASTObjects into a JSON AST
      """
      if validate:
          self.validate()
      return {
          "type": self.__class__.__name__,
          "chain": [op.to_json() for op in self.chain],
      }
  
file_path: pygraphistry/graphistry/compute/chain.py
imports: from typing import Any, Dict, Union, cast, List, Tuple, TYPE_CHECKING
  import pandas
  from graphistry.Engine import Engine, EngineAbstract, df_concat, resolve_engine
  from graphistry.Plottable import Plottable
  from graphistry.compute.ASTSerializable import ASTSerializable
  from graphistry.util import setup_logger
  from graphistry.utils.json import JSONVal
  from .ast import ASTObject, ASTNode, ASTEdge, from_json
  from .typing import DataFrameT
label_desc: Use image node_id 4 for calling the Chain obj's underlying member method code with example usage: obj.to_json(validate) and returns: dict