code: def get_query_string(request, new_params=None, remove=None):
      
      if new_params is None: new_params = {}
      if remove is None: remove = []
      p = dict(request.GET.items())
      for r in remove:
          for k in p.keys():
              if k.startswith(r):
                  del p[k]
      for k, v in new_params.items():
          if v is None:
              if k in p:
                  del p[k]
          else:
              p[k] = v
      return '?%s' % urlencode(p)
docs: Given the request, return the query string.
  
      Parameters can be added or removed as necessary.
  
      Code snippet taken from Django admin app (views/main.py)
  
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