docstr: Set trainable flag at the specified port.
  
  Parameters
  ----------
  port
      Port on which to set the trainable flag.
  
  value
      Trainable flag.
code: def set_trainable_at(self, port: int, value: bool):
      """Set trainable flag at the specified port.
  
      Parameters
      ----------
      port
          Port on which to set the trainable flag.
  
      value
          Trainable flag.
      """
      self._nodes[port].trainable = value
  
imports: import inspect
  import warnings
  from typing import Any, Callable, Dict, List, Optional, Union, TYPE_CHECKING
  from baikal._core.data_placeholder import DataPlaceholder, is_data_placeholder_list
  from baikal._core.utils import listify, make_name, make_repr
label_desc: Use image node_id 27 for calling the _StepBase obj's underlying member method code with example usage: obj.set_trainable_at(port, value) without return types