Returns the sha256 hash of the sorted content of the pyproject file.

def _get_content_hash(self):  # type: () -> str
        """
        Returns the sha256 hash of the sorted content of the pyproject file.
        """
        content = self._local_config

        relevant_content = {}
        for key in self._relevant_keys:
            relevant_content[key] = content.get(key)

        content_hash = sha256(
            json.dumps(relevant_content, sort_keys=True).encode()
        ).hexdigest()

        return content_hash