code: def remove_yaml_frontmatter(source, return_frontmatter=False):
      
      if source.startswith("---\n"):
          frontmatter_end = source.find("\n---\n", 4)
          if frontmatter_end == -1:
              frontmatter = source
              source = ""
          else:
              frontmatter = source[0:frontmatter_end]
              source = source[frontmatter_end + 5:]
          if return_frontmatter:
              return (source, frontmatter)
          return source
      if return_frontmatter:
          return (source, None)
      return source
docs: If there's one, remove the YAML front-matter from the source