class_docstr: Base class for missing values in supervised learning.
class_docstr_tok: ["Base","class","for","missing","values","in","supervised","learning","."]
docstr: Helper function
  Replace the first element of the column in the sframe with None.
docstr_tok: ["Helper","function","Replace","the","first","element","of","the","column","in","the","sframe","with","None","."]
code: def fill_some_na(self, sf, colname):
      """
      Helper function
      Replace the first element of the column in the sframe with None.
      """
      ret = sf.copy()
      if colname in sf.column_names():
          a = tc.SArray([None], sf[colname].dtype)
          b = sf[colname][1:]
          ret[colname] = a.append(b)
      return ret
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  import unittest
  import turicreate
  import array
  from turicreate.toolkits._main import ToolkitError
label_desc: Use image node_id 3 for calling the SupervisedLearningMissingValueTest obj's underlying member method code with example usage: obj.fill_some_na(sf, colname) and returns: ret