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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 _InitializeURL(self, upload_url, current_content_length):
 """Ensures that the URL used to upload operations is properly initialized. Args: upload_url: a string url. current_content_length: an integer identifying the current content length of data uploaded to the Batch Job. Returns: An initialized string URL, or the provided string URL if the URL has already been initialized. """

    # If initialization is not necessary, return the provided upload_url.
    if current_content_length != 0:
      return upload_url

    headers = {
        'Content-Type': 'application/xml',
        'Content-Length': 0,
        'x-goog-resumable': 'start'
    }

    # Send an HTTP POST request to the given upload_url
    req = urllib2.Request(upload_url, data={}, headers=headers)
    resp = self._url_opener.open(req)

    return resp.headers['location']