code: def hash_count(self, line, pound=None):
          
          if pound is None:
              pound = '#'
              
          count = 0
          for c in line:
              if c != pound:
                  break
              count += 1
  
          return count
docs: Count hashes (or other run of chars) at start of line
  
          >>> x = Mark2Slide()
          >>> x.hash_count('### hello')
          3
  
          >>> x = Mark2Slide()
          >>> x.hash_count(' hello', ' ')
          1