fix dict utils (#410)

* fix dict utils * fix dict utils

Author: arrjon

bayesflow/utils/dict_utils.py

@@ -222,7 +222,7 @@ def make_variable_array(
  else:
  raise TypeError(f"Only dicts and tensors are supported as arguments, but your estimates are of type {type(x)}")
 
- if len(variable_names) is not x.shape[-1]:
+ if len(variable_names) != x.shape[-1]:
  raise ValueError("Length of 'variable_names' should be the same as the number of variables.")
 
  if variable_keys is None: