docs: def clean_key_name(key):
      """
      Makes ``key`` a valid and appropriate SQL column name:
  
      1. Replaces illegal characters in column names with ``_``
  
      2. Prevents name from beginning with a digit (prepends ``_``)
  
      3. Lowercases name.  If you want case-sensitive table
      or column names, you are a bad person and you should feel bad.
      """
      result = _illegal_in_column_name.sub("_", key.strip())
      if result[0].isdigit():
          result = '_%s' % result
      if result.upper() in sql_reserved_words:
          result = '_%s' % key
      return result.lower()