<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _GetBetweenQEqualsAndAmpersand(self, url):
 """Retrieves the substring between the substrings 'q=' and '&'. Args: url (str):
 URL. Returns: str: search query, the value between 'q=' and '&' or None if no query was found. """

    # Make sure we're analyzing the query part of the URL.
    _, _, url = url.partition('?')
    # Look for a key value pair named 'q'.
    _, _, url = url.partition('q=')
    if not url:
      return ''

    # Strip additional key value pairs.
    url, _, _ = url.partition('&')
    return url