class_docstr: Adds missing values to a complete dataset.
  
  Attributes
  ----------
  data: np.ndarray
      Matrix of values with no NaN's that you want to add NaN's to.
  thr: float (optional)
      The percentage of null values you want in your dataset, a number
      between 0 and 1.
  
  Methods
  -------
  mcar()
      Overwrite values with MCAR placed NaN's.
  mar()
      Overwrite values with MAR placed NaN's.
  mnar()
      Overwrite values with MNAR placed NaN's.
code: def __init__(self, data, thr=0.2, dtype=np.float):
      self.dtype = data.dtype
      self.shape = np.shape(data)
      self.data = data.astype(dtype)
      self.thr = thr
  
imports: import numpy
label_desc: Use image node_id 1 to create a new Corruptor object  with example: obj = Corruptor(data, thr, dtype)