class_docstr: A Matplotlib converter class 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'
class_docstr_tok: ["A","Matplotlib","converter","class","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","'"]
code: def default_units(value, axis):
      # docstring inherited
      # The default behavior for string indexing.
      return "indexed"
  
imports: import numpy
  import matplotlib.units
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