[Cython] Fix external cantera cimport

interfaces/cython/cantera/__init__.pxd

@@ -1,4 +1,22 @@
 # This file is part of Cantera. See License.txt in the top-level directory or
 # at https://cantera.org/license.txt for license and copyright information.
 
-from cantera._cantera cimport *
+# Import content from individual .pxd files
+from cantera._onedim cimport *
+from cantera._utils cimport *
+from cantera.constants cimport *
+from cantera.ctcxx cimport *
+from cantera.delegator cimport *
+from cantera.func1 cimport *
+from cantera.kinetics cimport *
+from cantera.mixture cimport *
+from cantera.preconditioners cimport *
+from cantera.reaction cimport *
+from cantera.reactionpath cimport *
+from cantera.reactor cimport *
+from cantera.solutionbase cimport *
+from cantera.speciesthermo cimport *
+from cantera.thermo cimport *
+from cantera.transport cimport *
+from cantera.units cimport *
+from cantera.yamlwriter cimport *