added extra documentation

bilby/gw/likelihood/relative.py

@@ -23,7 +23,10 @@ class RelativeBinningGravitationalWaveTransient(GravitationalWaveTransient):
         given some set of parameters
     fiducial_parameters: dict, optional
         A starting guess for initial parameters of the event for finding the
-        maximum likelihood (fiducial) waveform.
+        maximum likelihood (fiducial) waveform. These should be specified in
+        the same parameter basis as the one that sampling is carried out in.
+        For example, if sampling in `mass_1` and `mass_2`, the fiducial
+        parameters should also be provided in `mass_1` and `mass_2.`
     parameter_bounds: dict, optional
         Dictionary of bounds (lists) for the initial parameters when finding
         the initial maximum likelihood (fiducial) waveform.

examples/gw_examples/data_examples/GW190425.py

@@ -32,6 +32,10 @@ start_time = end_time - duration
 # The fiducial parameters are taken to me the max likelihood sample from the
 # posterior sample release of LIGO-Virgo
 # https://www.gw-openscience.org/eventapi/html/O3_Discovery_Papers/GW190425/
+# The fiducial parameters should always be in provided in the same basis as
+# the sampling basis. For example, if sampling in  `mass_1` and `mass_2` instead of
+# `chirp_mass` and `mass_ratio`, the fiducial parameters should also be provided in
+# `mass_1` and `mass_2` below.
 
 fiducial_parameters = {
     "a_1": 0.018,