code: def make_placeholders(seq, start=1):
      
      if len(seq) == 0:
          raise ValueError('Sequence must have at least one element.')
      param_style = Context.current().param_style
      placeholders = None
      if isinstance(seq, dict):
          if param_style in ('named', 'pyformat'):
              template = ':%s' if param_style == 'named' else '%%(%s)s'
              placeholders = (template % key
                              for key in six.iterkeys(seq))
      elif isinstance(seq, (list, tuple)):
          if param_style == 'numeric':
              placeholders = (':%d' % i
                              for i in xrange(start, start + len(seq)))
          elif param_style in ('qmark', 'format', 'pyformat'):
              placeholders = itertools.repeat(
                  '?' if param_style == 'qmark' else '%s',
                  len(seq))
      if placeholders is None:
          raise NotSupported(
              "Param style '%s' does not support sequence type '%s'" % (
                  param_style, seq.__class__.__name__))
      return ', '.join(placeholders)
docs: Generate placeholders for the given sequence.