How to build a generating series

edit

Hello. Forgive me, I'm still a bit new to coding. I want to create a generating q-series for functions I've already defined, which have complex number outputs. These functions are denoted g(k, n, z), where k, n are integers and z in a complex input. I'd like the series sum([g(k, n, z)*q^n for n in range(1, 100)]) or something along those lines. The error code is:

`---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-35-5dc58c06413b> in <module>
      5     return sum([g(k, n, z)*q**n for n in range(Integer(1), Integer(100))])
      6 
----> 7 G(Integer(2), Integer(1)+i)

<ipython-input-35-5dc58c06413b> in G(k, z)
      3 def G(k, z):
      4     var('q')
----> 5     return sum([g(k, n, z)*q**n for n in range(Integer(1), Integer(100))])
      6 
      7 G(Integer(2), Integer(1)+i)
<ipython-input-35-5dc58c06413b> in <listcomp>(.0)
      3 def G(k, z):
      4     var('q')
----> 5     return sum([g(k, n, z)*q**n for n in range(Integer(1), Integer(100))])
      6 
      7 G(Integer(2), Integer(1)+i)
TypeError: unsupported operand type(s) for *: 'NoneType' and 'sage.symbolic.expression.Expression`

I apologize I cannot make the above formatting more clear. Perhaps someone could help me! Edit: Thank you for editing above error code!