input: Write a function to parse tags from Jekyll blog posts.
  assert parse_tags(['tags: python code'])==['python', 'code']
  assert parse_tags(['tags: travel adventure'])==['travel', 'adventure']
  assert parse_tags(['tags: tech', 'tags: programming'])==['tech', 'programming']
output: def parse_tags(lines):
      tags = []
      for line in lines:
          if line.startswith('tags:'):
              tags.extend(line[5:].strip().split())
      return tags