code: def __call__(self, groupby):
      df = groupby
      while df.op.output_types[0] not in (
          OutputType.dataframe,
          OutputType.series,
      ):
          df = df.inputs[0]
  
      selection = groupby.op.groupby_params.pop("selection", None)
      if df.ndim > 1 and selection:
          if (
              isinstance(selection, tuple)
              and selection not in df.dtypes
          ):
              selection = list(selection)
  
          result_df = df[selection]
      else:
          result_df = df
  
      self._output_types = (
          [OutputType.dataframe]
          if result_df.ndim == 2
          else [OutputType.series]
      )
  
      params = result_df.params
      params["shape"] = (np.nan,) + result_df.shape[1:]
      if isinstance(df.index_value.value, IndexValue.RangeIndex):
          params["index_value"] = parse_index(pd.RangeIndex(-1), df.key)
  
      return self.new_tileable([df], **params)
  
file_path: mars/mars/dataframe/groupby/head.py
imports: import numpy
  import pandas
  from ...None import opcodes
  from ...core import OutputType, get_output_types, recursive_tile
  from ...serialization.serializables import DictField, Int64Field, BoolField
  from ...utils import pd_release_version
  from ..core import IndexValue
  from ..operands import DataFrameOperandMixin, DataFrameOperand
  from ..utils import build_concatenated_rows_frame, parse_index
label_desc: Use image node_id 1 for calling the GroupByHead obj's underlying member method code with example usage: obj.__call__(groupby) and returns: self