@staticmethod
def contains_anchor(markdown: str, anchor: str) -> bool:
    """Check if a set of Markdown source text contains a heading that corresponds to a
    given anchor."""
    for line in markdown.splitlines():
        # Markdown allows whitespace before headers and an arbitrary number of #'s.
        heading_match = HEADING_PATTERN.match(line)
        if heading_match is not None:
            heading = heading_match.groups()[0]

            # Headings are allowed to have images after them, of the form:
            # # Heading [![Image](image-link)] or ![Image][image-reference]
            # But these images are not included in the generated anchor, so remove them.
            heading = re.sub(IMAGE_PATTERN, '', heading)
            anchor_slug = slugify(heading, '-')
            if anchor == anchor_slug:
                return True

        link_match = HTML_LINK_PATTERN.match(line)
        if link_match is not None and link_match.group(1) == anchor:
            return True

    return False