old_contents: """Base class for all filters."""
  #Author: Miguel Molero <miguel.molero@gmail.com>
  # License: BSD 3 clause
  
  from vtk import vtkPolyData
  
  from ..base import BaseObject
  
  class FilterBase(BaseObject):
      """
      Base Class for all Filter Objects
  
      Attributes
      ----------
      input_: vtkPolyData
          Input Data  to be filtered
  
      output_: vtkPolyData
          Output Data
  
      """
  
      def __init__(self):
  
          self.input_ = None
          self.output_ = None
  
      def set_input(self, input_data):
  
          """
          set input data
  
          Parameters
          ----------
          input-data : vtkPolyData
  
          Returns
          -------
          is_valid: bool
              Returns True if the input_data is valid for processing
  
          """
          if isinstance(input_data, vtkPolyData):
              return True
          else:
              return False
  
  
      def get_output(self):
  
          if self.output_:
              return self.output_
  
      def update(self):
          pass
  
  
new_contents: """Base class for all filters."""
  #Author: Miguel Molero <miguel.molero@gmail.com>
  # License: BSD 3 clause
  
  from vtk import vtkPolyData
  
  from ..base import BaseObject
  
  class FilterBase(BaseObject):
      """
      Base Class for all Filter Objects
  
      Attributes
      ----------
      input_: vtkPolyData
          Input Data  to be filtered
  
      output_: vtkPolyData
          Output Data
  
      """
  
      def __init__(self):
  
          self.input_ = None
          self.output_ = None
  
      def set_input(self, input_data):
  
          """
          set input data
  
          Parameters
          ----------
          input-data : vtkPolyData
  
          Returns
          -------
          is_valid: bool
              Returns True if the input_data is valid for processing
  
          """
          if isinstance(input_data, vtkPolyData):
              self.input_ = input_data
              return True
          else:
              return False
  
  
      def get_output(self):
  
          if self.output_:
              return self.output_
  
      def update(self):
          pass
  
  
subject: fix input data asssigment