code: def _get_shape(cls, input_shape, op):
      shape = (np.nan,) + input_shape[1:]
      if op.output_types[0] == OutputType.dataframe and len(shape) == 1:
          shape += (3,)
      return shape
  
imports: import numpy
  import pandas
  from ...None import opcodes
  from ...core.operand import OperandStage
  from ...serialization.serializables import BoolField
  from ...utils import lazy_import, calc_nsplits
  from ..operands import OutputType
  from ..utils import parse_index, hash_dataframe_on, gen_unknown_index_value, standardize_range_index
  from ._duplicate import DuplicateOperand, validate_subset
label_desc: Use image node_id 3 for calling the DataFrameDropDuplicates obj's underlying member method code with example usage: obj._get_shape(cls, input_shape, op) and returns: shape