updated docs as well

Author: mitzimorris

cmdstanpy/stanfit/mcmc.py

@@ -448,11 +448,11 @@ def summary(
     ) -> pd.DataFrame:
         """
         Run cmdstan/bin/stansummary over all output CSV files, assemble
-        summary into DataFrame object; first row contains summary statistics
-        for total joint log probability `lp__`, remaining rows contain summary
+        summary into DataFrame object.  The first row contains statistics
+        for the total joint log probability `lp__`, but is omitted when the
+        Stan model has no parameters.  The remaining rows contain summary
         statistics for all parameters, transformed parameters, and generated
-        quantities variables listed in the order in which they were declared
-        in the Stan program.
+        quantities variables, in program declaration order.
 
         :param percentiles: Ordered non-empty sequence of percentiles to report.
             Must be integers from (1, 99), inclusive. Defaults to