I believe exceptions due to type errors when trying to parse the wrong datatype should be more clear.
I recently ran into a situation whereby I was inadvertently passing a PhoneNumber object type to the parse function. This resulted in the following error:
AttributeError: 'PhoneNumber' object has no attribute 'find'

Despite the fact I was passing a PhoneNumber object, it was not obvious to me in the moment that I needed to be passing a string based on the exception, which sent me investigating why that object lacked the attribute being called instead of letting me know that I was experiencing a TypeError and that the function was expecting a string in the first place.
This becomes more ambiguous if a user feeds the function an int, (which seems a much more likely mistake) which returns the following exception:
TypeError: object of type 'int' has no len()

The following code produces these exceptions depending on what is printed:

import phonenumbers

phone_number_int = 1111111111
phone_number_str = str(phone_number_int)
phone_number_object = phonenumbers.parse(phone_number_str, 'US')
phone_number_error = phonenumbers.parse(phone_number_int)

print(phone_number_error)

I believe a simple check of the number variable that raises a TypeError if not a string type and lets the user know the function is expecting a string would be helpful, and I would be happy to raise a pull request with this change.

Thank you.