class_docstr: Iterator for creating Quantile DMatrix from partitions.
code: def next(self, input_data: Callable) -> int:
      if self._iter == len(self._data[alias.data]):
          return 0
      input_data(
          data=self._fetch(self._data[alias.data]),
          label=self._fetch(self._data.get(alias.label, None)),
          weight=self._fetch(self._data.get(alias.weight, None)),
          base_margin=self._fetch(self._data.get(alias.margin, None)),
          qid=self._fetch(self._data.get(alias.qid, None)),
          **self._kwargs,
      )
      self._iter += 1
      return 1
  
imports: from collections import defaultdict, namedtuple
  from typing import Any, Callable, Dict, Iterator, List, Optional, Sequence, Tuple, Union
  import numpy
  import pandas
  from scipy.sparse import csr_matrix
  from xgboost import DataIter, DMatrix, QuantileDMatrix, XGBModel
  from xgboost.compat import concat
  from .._typing import ArrayLike
  from .utils import get_logger
label_desc: Use image node_id 3 for calling the PartIter obj's underlying member method code with example usage: obj.next(input_data) and returns: int, int