code: def default_unit_label(axis, unit):
      
      if not axis.isDefault_label:
          return
      label = axis.set_label_text(unit.to_string('latex_inline_dimensional'))
      axis.isDefault_label = True
      return label.get_text()
docs: Set default label for an axis from a `~astropy.units.Unit`
  
      If the axis already has a label, this function does nothing.
  
      Parameters
      ----------
      axis : `~matplotlib.axis.Axis`
          the axis to manipulate
  
      unit : `~astropy.units.Unit`
          the unit to use for the label
  
      Returns
      -------
      text : `str`, `None`
          the text for the new label, if set, otherwise `None`