code: def _convert_unit(unit):
      
      if unit is None:
          return ''
  
      prefix = None
      suffix = None
      if unit[:5].lower() == 'milli':
          prefix = 'm'
          unit = unit[5:]
      elif unit[:5].lower() == 'micro':
          prefix = mu
          unit = unit[5:]
      elif unit[:2].lower() == 'mu':
          prefix = mu
          unit = unit[2:]
  
      if unit[-4:].lower() == 'volt':
          suffix = 'V'
          unit = unit[:-4]
  
      if prefix is None and suffix is None:
          unit = unit
      elif prefix is None and suffix is not None:
          unit = unit + suffix
      elif prefix is not None and suffix is None:
          unit = prefix + unit
      else:
          unit = prefix + suffix
  
      return unit
docs: Convert different names into SI units.
  
      Parameters
      ----------
      unit : str
          unit to convert to SI
  
      Returns
      -------
      str
          unit in SI format.
  
      Notes
      -----
      SI unit such as mV (milliVolt, mVolt), μV (microVolt, muV).