comment about fixed representation

Author: volodymyrss

astroquery/heasarc/core.py

@@ -169,6 +169,8 @@ def query_region_async(self, position: Union[coordinates.SkyCoord, str],
         kwargs['equinox'] = 2000
 
         # Generate the request
+        # Fixed string representation of coordinates ensures that request payload
+        # does not depend on python/astropy version for the same input coordinates
         request_payload = self._args_to_payload(
             mission=mission,
             entry=f"{c.ra.degree:.10f},{c.dec.degree:.10f}",