code: def _add_dep_doc(old_doc, dep_doc):
      """Add deprecation message `dep_doc` to docstring in `old_doc`.
  
      Parameters
      ----------
      old_doc : str
          Docstring from some object.
      dep_doc : str
          Deprecation warning to add to top of docstring, after initial line.
  
      Returns
      -------
      new_doc : str
          `old_doc` with `dep_doc` inserted after any first lines of docstring.
  
      """
      dep_doc = _ensure_cr(dep_doc)
      if not old_doc:
          return dep_doc
      old_doc = _ensure_cr(old_doc)
      old_lines = old_doc.splitlines()
      new_lines = []
      for line_no, line in enumerate(old_lines):
          if line.strip():
              new_lines.append(line)
          else:
              break
      next_line = line_no + 1
      if next_line >= len(old_lines):
          # nothing following first paragraph, just append message
          return old_doc + "\n" + dep_doc
      indent = _LEADING_WHITE.match(old_lines[next_line]).group()
      dep_lines = [
          indent + L for L in [""] + dep_doc.splitlines() + [""]
      ]
      return (
          "\n".join(new_lines + dep_lines + old_lines[next_line:])
          + "\n"
      )
  
file_path: dipy/dipy/utils/deprecator.py
imports: import functools
  import warnings
  import re
  from inspect import signature
  from dipy import __version__
  from packaging.version import parse
label_desc: Use image node_id 2 for calling a global function with example usage: _add_dep_doc(old_doc, dep_doc) and returns: unknown, dep_doc, unknown