code: def sqlalchemy_escape(val, escape_char, special_chars):
      
      if sys.version_info[:2] >= (3, 0):
          assert isinstance(val, str)
      else:
          assert isinstance(val, basestring)
      result = []
      for c in val:
          if c in special_chars + escape_char:
              result.extend(escape_char + c)
          else:
              result.extend(c)
      return ''.join(result)
docs: Escape a string according for use in LIKE operator
  
      >>> sqlalchemy_escape("text_table", "\\", "%_")
      'text\_table'