code: def kvpath(self, base, *pa, **kw):
          
          def fmt(vtuple):
              typ, val = vtuple
              if not val is None:
                  return safeformat("{:%s}"%typ, val)
              return None
          parts = [base]
          for v in pa:
              fv = fmt(v)
              if not fv is None:
                  parts.append(quote(fv))
          for k,v in kw.items():
              fv = fmt(v)
              if not fv is None:
                  parts.append(quote(k+"="+fv))
          return "/".join(parts)
docs: Key-value query url builder (of the form: "base/v0/k1=v1/k2=v2").