code: def read_ray_mldataset(mldataset, **kwargs):
      import ray.util.data
  
      assert isinstance(mldataset, ray.util.data.MLDataset)
      not_empty_dfs = mldataset.filter(lambda df: len(df) > 0).take(1)
      if not not_empty_dfs:
          raise ValueError(
              f"MLDataset {mldataset} is empty, please provide an non-empty dataset."
          )
      df_record: pd.DataFrame = not_empty_dfs[0]
      columns = df_record.columns.names
      nrows = sum(mldataset.for_each(lambda df: len(df)).gather_async())
      op = DataFrameReadMLDataset(
          mldataset=mldataset, columns=columns, nrows=nrows
      )
      return op(df_record.dtypes, nrows)
  
imports: import functools
  import warnings
  import numpy
  import pandas
  from ...None import opcodes
  from ...core import OutputType
  from ...serialization.serializables import AnyField, BoolField, ListField, Int64Field, ReferenceField
  from ..utils import parse_index, lazy_import, tokenize
  from .core import IncrementalIndexDatasource, IncrementalIndexDataSourceMixin, HeadOptimizedDataSource
label_desc: Use image node_id 3 for calling a global function with example usage: read_ray_mldataset(mldataset) and returns: op