code: def format_base64(data):
    
  
    try:
      return binascii.b2a_base64(data).decode('utf-8').rstrip('=\n ')
  
    except (TypeError, binascii.Error) as e:
      raise securesystemslib.exceptions.FormatError('Invalid base64'
        ' encoding: ' + str(e))
docs: <Purpose>
      Return the base64 encoding of 'data' with whitespace and '=' signs omitted.
  
    <Arguments>
      data:
        Binary or buffer of data to convert.
  
    <Exceptions>
      securesystemslib.exceptions.FormatError, if the base64 encoding fails or the
      argument is invalid.
  
    <Side Effects>
      None.
  
    <Returns>
      A base64-encoded string.