Running this on Python2.7
First error AttributeError: 'str' object has no attribute 'isnumeric', quick fix convert string into unicode.
Second error: AttributeError: 'list' object has no attribute 'copy', quick fix use below for python2.7

    #tokens = tokens.copy()
    tokens = tokens[:]

Third error: AssertionError: Classes must either be a tuple or a type., for queries which contain date-time but in string(now unicode) format along with other unessential data, such as, "show me flights to london in next week"