code: def lower(s: "Stream[str]") -> "Stream[str]":
      """Computes the lowercase of a string stream.
  
      Parameters
      ----------
      s : `Stream[str]`
          A string stream.
  
      Returns
      -------
      `Stream[str]`
          A lowercase string stream.
      """
      return s.apply(lambda x: x.lower()).astype("string")
  
file_path: tensortrade/tensortrade/feed/api/string/operations.py
imports: from tensortrade.feed.core.base import Stream
  from tensortrade.feed.api.string import String
label_desc: Use image node_id 3 for calling a global function with example usage: lower(s) and returns: s