Support annotated assignments within class definition in LocalPythonExecutor

[albertvillanova]

Support annotated assignments within class definition in LocalPythonExecutor.

This will allow pydantic code:

from pydantic import BaseModel, Field                                                                                                                                         
                                                                                                                                                                                
  class MarkdownFile(BaseModel):                                                                                                                                                
      path: str = Field(description="The path to the markdown file")

Fix #1352.

[aymeric-roucher]

Nice addition! Thanks! 😃