class_docstr: Abstract class representing a source of inputs for LLMFunction.
  
  This class could be extended with concrete implementations that read data
  from external sources, such as Google Sheets.
code: def __init__(self):
      self._cached_inputs: NormalizedInputsList | None = None
      self._display_status_fn: Callable[[], None] = lambda: None
  
imports: from __future__ import annotations
  import abc
  from typing import Callable, Mapping, Sequence
label_desc: Use image node_id 1 to create a new LLMFnInputsSource object from inherited base classes: abc with example: obj = LLMFnInputsSource()