Fixed error handling in MetabolicNetwork.from_sbml

[AdityaTaggar05]

Initially, using an 'and' clause raised a TypeError when passing in a non-subscriptable data type; hence, the desired Exception was not raised. Due to the usage of 'or' clause in other '.from_' methods, it only checked the datatype and did not check the subscriptable nature, and raised the correct Exception. The image below demonstrates it.