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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 sanitize_metadata(self, metadata, replace_hyphen_with="-"):
 """Convert non-string metadata values to strings and drop null values"""

        return {str(k).replace("-", replace_hyphen_with): str(v)
                for k, v in (metadata or {}).items() if v is not None}