class_docstr: : A matplotlib converter class.  Provides matplotlib conversion
       functionality for string data values.
  
  Valid units for string are:
  - 'indexed' : Values are indexed as they are specified for plotting.
  - 'sorted'  : Values are sorted alphanumerically.
  - 'inverted' : Values are inverted so that the first value is on top.
  - 'sorted-inverted' :  A combination of 'sorted' and 'inverted'
docstr: : Return the default unit for value, or None.
  
  = INPUT VARIABLES
  - axis    The axis using this converter.
  - value   The value or list of values that need units.
  
  = RETURN VALUE
  - Returns the default units to use for value.
  Return the default unit for value, or None.
code: def default_units(value, axis):
      """: Return the default unit for value, or None.
  
      = INPUT VARIABLES
      - axis    The axis using this converter.
      - value   The value or list of values that need units.
  
      = RETURN VALUE
      - Returns the default units to use for value.
      Return the default unit for value, or None.
      """
  
      # The default behavior for string indexing.
      return "indexed"
  
file_path: catboost/contrib/python/matplotlib/py2/matplotlib/testing/jpl_units/StrConverter.py
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import six
  from six.moves import xrange
  import matplotlib.units
  from matplotlib.cbook import iterable
label_desc: Use image node_id 3 for calling the StrConverter obj's underlying member method code with example usage: obj.default_units(value, axis) and returns: str