docstr: Return the call signature for any callable object.
  
  If any exception is generated, None is returned instead and the
  exception is suppressed.
code: def _getdef(self, obj, oname=""):
      """Return the call signature for any callable object.
  
      If any exception is generated, None is returned instead and the
      exception is suppressed."""
      try:
          hdef = oname + str(signature(obj))
          return cast_unicode(hdef)
      except:
          return None
  
imports: from __future__ import print_function
  import inspect
  import linecache
  import warnings
  import os
  from textwrap import dedent
  import types
  import io
  from IPython.core import page
  from IPython.lib.pretty import pretty
  from IPython.testing.skipdoctest import skip_doctest_py3
  from IPython.utils import PyColorize
  from IPython.utils import openpy
  from IPython.utils import py3compat
  from IPython.utils.dir2 import safe_hasattr
  from IPython.utils.path import compress_user
  from IPython.utils.text import indent
  from IPython.utils.wildcard import list_namespace
  from IPython.utils.coloransi import TermColors, ColorScheme, ColorSchemeTable
  from IPython.utils.py3compat import cast_unicode, string_types, PY3
  from IPython.utils.signatures import signature
  from IPython.utils.colorable import Colorable
  from pygments import highlight
  from pygments.formatters import HtmlFormatter
label_desc: Use image node_id 2 for calling the Inspector obj's underlying member method code with example usage: obj._getdef(obj, oname) and returns: cast_unicode, None