Generate a listing of the given type of problems.

    Args:
      problem_type: The type of problem. This is one of the problem type
                    constants from transitfeed.

    Returns:
      The generated HTML as a string.

def _GenerateSection(self, problem_type):
    """Generate a listing of the given type of problems.

    Args:
      problem_type: The type of problem. This is one of the problem type
                    constants from transitfeed.

    Returns:
      The generated HTML as a string.
    """
    if problem_type == transitfeed.TYPE_WARNING:
      dataset_problems = self._dataset_warnings
      heading = 'Warnings'
    else:
      dataset_problems = self._dataset_errors
      heading = 'Errors'

    if not dataset_problems:
      return ''

    prefix = '<h2 class="issueHeader">%s:</h2>' % heading
    dataset_sections = []
    for dataset_merger, problems in dataset_problems.items():
      dataset_sections.append('<h3>%s</h3><ol>%s</ol>' % (
          dataset_merger.FILE_NAME, '\n'.join(problems)))
    body = '\n'.join(dataset_sections)
    return prefix + body