Adding function for mutable coords (#6515)

* adding function for mutable coords

* Added coords_mutable

* add coords_mutable

* Make `coords_mutable` an explicit kwarg

* Remove reference to undefined variable

* Adding an if block

---------

Co-authored-by: Michael Osthege <michael.osthege@outlook.com>

Author: Dhruvanshu-Joshi

pymc/model.py

@@ -550,6 +550,7 @@ def __init__(
         coords=None,
         check_bounds=True,
         *,
+        coords_mutable=None,
         pytensor_config=None,
         model=None,
     ):
@@ -586,6 +587,9 @@ def __init__(
             self._coords = {}
             self._dim_lengths = {}
         self.add_coords(coords)
+        if coords_mutable is not None:
+            for name, values in coords_mutable.items():
+                self.add_coord(name, values, mutable=True)
 
         from pymc.printing import str_for_model