How to use the xonsh.tools.cast_unicode function in xonsh

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 + inspect.signature(*getargspec(obj))
            return cast_unicode(hdef)
        except:  # pylint:disable=bare-except
            return None

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 + inspect.signature(*getargspec(obj))
            return cast_unicode(hdef)
        except:  # pylint:disable=bare-except
            return None

allows objects which provide their docstrings via non-standard mechanisms
    (like Pyro proxies) to still be inspected by ipython's ? system."""
    # Allow objects to offer customized documentation via a getdoc method:
    try:
        ds = obj.getdoc()
    except Exception:  # pylint:disable=broad-except
        pass
    else:
        # if we get extra info, we add it to the normal docstring.
        if isinstance(ds, str):
            return inspect.cleandoc(ds)

    try:
        docstr = inspect.getdoc(obj)
        encoding = get_encoding(obj)
        return cast_unicode(docstr, encoding=encoding)
    except Exception:  # pylint:disable=broad-except
        # Harden against an inspect failure, which can occur with
        # SWIG-wrapped extensions.
        raise

fname = None
    try:
        fname = inspect.getabsfile(obj)
    except TypeError:
        # For an instance, the file that matters is where its class was
        # declared.
        if hasattr(obj, "__class__"):
            try:
                fname = inspect.getabsfile(obj.__class__)
            except TypeError:
                # Can happen for builtins
                pass
    except:  # pylint:disable=bare-except
        pass
    return cast_unicode(fname)

This implementation will skip returning any output for binary objects,
      but custom extractors may know how to meaningfully process them."""

    if is_binary:
        return None
    else:
        # get source if obj was decorated with @decorator
        if hasattr(obj, "__wrapped__"):
            obj = obj.__wrapped__
        try:
            src = inspect.getsource(obj)
        except TypeError:
            if hasattr(obj, "__class__"):
                src = inspect.getsource(obj.__class__)
        encoding = get_encoding(obj)
        return cast_unicode(src, encoding=encoding)

allows objects which provide their docstrings via non-standard mechanisms
    (like Pyro proxies) to still be inspected by ipython's ? system."""
    # Allow objects to offer customized documentation via a getdoc method:
    try:
        ds = obj.getdoc()
    except Exception:  # pylint:disable=broad-except
        pass
    else:
        # if we get extra info, we add it to the normal docstring.
        if isinstance(ds, str):
            return inspect.cleandoc(ds)

    try:
        docstr = inspect.getdoc(obj)
        encoding = get_encoding(obj)
        return cast_unicode(docstr, encoding=encoding)
    except Exception:  # pylint:disable=broad-except
        # Harden against an inspect failure, which can occur with
        # SWIG-wrapped extensions.
        raise