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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def remove_yaml_frontmatter(source, return_frontmatter=False):
 """If there's one, remove the YAML front-matter from the source """

    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