code: def _compute(self, arrays, dates, assets, mask):
          
          out = full(mask.shape, self.missing_value, dtype=self.dtype)
          # This writes directly into our output buffer.
          numexpr.evaluate(
              self._expr,
              local_dict={
                  "x_%d" % idx: array
                  for idx, array in enumerate(arrays)
              },
              global_dict={'inf': inf},
              out=out,
          )
          return out
docs: Compute our stored expression string with numexpr.