class_docstr: An operator that has one input and one output dependency.
  
  This operator serves as the base for map, filter, limit, etc.
code: def input_dependency(self) -> PhysicalOperator:
      return self.input_dependencies[0]
  
imports: from typing import List, Optional
  from ray.data._internal.execution.interfaces import AllToAllTransformFn, PhysicalOperator, RefBundle, TaskContext
  from ray.data._internal.logical.interfaces import LogicalOperator
  from ray.data._internal.progress_bar import ProgressBar
  from ray.data._internal.stats import StatsDict
label_desc: Use image node_id 2 for calling the OneToOneOperator obj's underlying member method code with example usage: obj.input_dependency() and returns: self