Use tuples throughout _get_bc_params

Update distributions to pass tuples to _get_bc_params

sktime/proba/base.py

@@ -158,17 +158,17 @@ def _method_error_msg(self, method="this method", severity="warn", fill_in=None)
         else:
             return msg
 
-    def _get_bc_params(self, to_broadcast, dtype=None):
-        """Fully broadcast parameters of self, given param shapes and index, columns."""
-        length = len(to_broadcast)
+    def _get_bc_params(self, *args, dtype=None):
+        """Fully broadcast tuple of parameters given param shapes and index, columns."""
+        number_of_params = len(args)
         if hasattr(self, "index") and self.index is not None:
-            to_broadcast += [self.index.to_numpy().reshape(-1, 1)]
+            args += tuple(self.index.to_numpy().reshape(-1, 1))
         if hasattr(self, "columns") and self.columns is not None:
-            to_broadcast += [self.columns.to_numpy()]
-        bc = np.broadcast_arrays(*to_broadcast)
+            args += tuple(self.columns.to_numpy())
+        bc = np.broadcast_arrays(*args)
         if dtype is not None:
             bc = [array.astype(dtype) for array in bc]
-        return bc[:length]
+        return bc[:number_of_params]
 
     def pdf(self, x):
         r"""Probability density function.

sktime/proba/normal.py

@@ -45,7 +45,7 @@ def __init__(self, mu, sigma, index=None, columns=None):
         # and broadcast of parameters.
         # move this functionality to the base class
         # 0.19.0?
-        self._mu, self._sigma = self._get_bc_params([self.mu, self.sigma])
+        self._mu, self._sigma = self._get_bc_params(*(self.mu, self.sigma))
         shape = self._mu.shape
 
         if index is None:

sktime/proba/t.py

@@ -45,7 +45,7 @@ def __init__(self, mu, sigma, df=1, index=None, columns=None):
         self.columns = columns
 
         self._mu, self._sigma, self._df = self._get_bc_params(
-            [self.mu, self.sigma, self.df]
+            *(self.mu, self.sigma, self.df)
         )
         shape = self._mu.shape
 

sktime/proba/tests/test_base_default_methods.py

@@ -34,7 +34,7 @@ def __init__(self, mu, sigma, index=None, columns=None):
         self.index = index
         self.columns = columns
 
-        self._mu, self._sigma = self._get_bc_params([self.mu, self.sigma])
+        self._mu, self._sigma = self._get_bc_params(*(self.mu, self.sigma))
         shape = self._mu.shape
 
         if index is None:

sktime/proba/tfp.py

@@ -53,7 +53,7 @@ def __init__(self, mu, sigma, index=None, columns=None):
         # move this functionality to the base class
         # 0.19.0?
         self._mu, self._sigma = self._get_bc_params(
-            [self.mu, self.sigma], dtype="float"
+            *(self.mu, self.sigma), dtype="float"
         )
         distr = tfd.Normal(loc=self._mu, scale=self._sigma)
         shape = self._mu.shape