code: def CheckUpperLowerCase(filename, linenumber, clean_lines, errors):
      
      line = clean_lines.lines[linenumber]
      if ContainsCommand(line):
          command = GetCommand(line)
          if IsCommandMixedCase(command):
              return errors(
                      filename,
                      linenumber,
                      'readability/wonkycase',
                      'Do not use mixed case commands')
          if clean_lines.have_seen_uppercase is None:
              clean_lines.have_seen_uppercase = IsCommandUpperCase(command)
          else:
              is_upper = IsCommandUpperCase(command)
              if is_upper != clean_lines.have_seen_uppercase:
                  return errors(
                          filename,
                          linenumber,
                          'readability/mixedcase',
                          'Do not mix upper and lower case commands')
docs: Check that commands are either lower case or upper case, but not both