fix SyntaxWarning by making some docstrings raw

Author: drbenvincent

causalpy/pymc_models.py

@@ -184,7 +184,7 @@ def print_row(
 
 
 class LinearRegression(PyMCModel):
-    """
+    r"""
     Custom PyMC model for linear regression.
 
     Defines the PyMC model
@@ -230,7 +230,7 @@ def build_model(self, X, y, coords):
 
 
 class WeightedSumFitter(PyMCModel):
-    """
+    r"""
     Used for synthetic control experiments.
 
     Defines the PyMC model:
@@ -423,7 +423,7 @@ def fit(self, X, Z, y, t, coords, priors, ppc_sampler=None):
 
 
 class PropensityScore(PyMCModel):
-    """
+    r"""
     Custom PyMC model for inverse propensity score models
 
     .. note: