code: def _do_code_blocks(self, text):
          
          code_block_re = re.compile(r'''
              (?:\n\n|\A\n?)
              (               # $1 = the code block -- one or more lines, starting with a space/tab
                (?:
                  (?:[ ]{%d} | \t)  # Lines must start with a tab or a tab-width of spaces
                  .*\n+
                )+
              )
              ((?=^[ ]{0,%d}\S)|\Z)   # Lookahead for non-space at line-start, or end of doc
              ''' % (self.tab_width, self.tab_width),
              re.M | re.X)
          return code_block_re.sub(self._code_block_sub, text)
docs: Process Markdown `<pre><code>` blocks.