<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _convert_to_indexer(self, obj, axis=None, is_setter=False, raise_missing=False):
 """ Convert indexing key into something we can use to do actual fancy indexing on an ndarray Examples ix[:5] -> slice(0, 5) ix[[1,2,3]] -> [1,2,3] ix[['foo', 'bar', 'baz']] -> [i, j, k] (indices of foo, bar, baz) Going by Zen of Python? 'In the face of ambiguity, refuse the temptation to guess.' raise AmbiguousIndexError with integer labels? - No, prefer label-based indexing """

        if axis is None:
            axis = self.axis or 0

        labels = self.obj._get_axis(axis)

        if isinstance(obj, slice):
            return self._convert_slice_indexer(obj, axis)

        # try to find out correct indexer, if not type correct raise
        try:
            obj = self._convert_scalar_indexer(obj, axis)
        except TypeError:

            # but we will allow setting
            if is_setter:
                pass

        # see if we are positional in nature
        is_int_index = labels.is_integer()
        is_int_positional = is_integer(obj) and not is_int_index

        # if we are a label return me
        try:
            return labels.get_loc(obj)
        except LookupError:
            if isinstance(obj, tuple) and isinstance(labels, MultiIndex):
                if is_setter and len(obj) == labels.nlevels:
                    return {'key': obj}
                raise
        except TypeError:
            pass
        except (ValueError):
            if not is_int_positional:
                raise

        # a positional
        if is_int_positional:

            # if we are setting and its not a valid location
            # its an insert which fails by definition
            if is_setter:

                # always valid
                if self.name == 'loc':
                    return {'key': obj}

                # a positional
                if (obj >= self.obj.shape[axis] and
                        not isinstance(labels, MultiIndex)):
                    raise ValueError("cannot set by positional indexing with "
                                     "enlargement")

            return obj

        if is_nested_tuple(obj, labels):
            return labels.get_locs(obj)

        elif is_list_like_indexer(obj):

            if com.is_bool_indexer(obj):
                obj = check_bool_indexer(labels, obj)
                inds, = obj.nonzero()
                return inds
            else:
                # When setting, missing keys are not allowed, even with .loc:
                kwargs = {'raise_missing': True if is_setter else
                          raise_missing}
                return self._get_listlike_indexer(obj, axis, **kwargs)[1]
        else:
            try:
                return labels.get_loc(obj)
            except LookupError:
                # allow a not found key only if we are a setter
                if not is_list_like_indexer(obj) and is_setter:
                    return {'key': obj}
                raise