Removed redundant default value for alpha

[MarcusHaggbom]

Backwards compatible
No new functionality
Note! Test function was modified to use a value of alpha=5.

Removed default value for alpha parameter everywhere in filter_bank.py except factory function (scattering_filter_factory). This way the value of alpha is set once, avoiding a possible override of this value by the default.

[lostanlen]

@janden how can i restart this CI so that we retry the build on Jenkins?
and how do i run "self-hosted CI" ?

[janden]

I have rebased this on top of the new dev, so the CI should be working again.

[janden]

@MarcusHaggbom Remind me again what alpha does and why it's redundant?

[codecov-commenter]

Codecov Report

Merging #814 (d6f7816) into dev (ca9073f) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##              dev     #814   +/-   ##
=======================================
  Coverage   88.03%   88.03%           
=======================================
  Files          64       64           
  Lines        2323     2323           
=======================================
  Hits         2045     2045           
  Misses        278      278           

Flag	Coverage Δ
jenkins_main	88.03% <100.00%> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
kymatio/scattering1d/utils.py	100.00% <ø> (ø)
kymatio/scattering1d/filter_bank.py	100.00% <100.00%> (ø)

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[MarcusHaggbom]

@MarcusHaggbom Remind me again what alpha does and why it's redundant?

Alpha works as a parameter on how much aliasing error is tolerated when subsampling, and hence affects the number of "allowed" dyadic subsamplings for a wavelet.
The redundancy comes from assigning a default value to alpha in multiple places; when querying for filters given a certain value for alpha, this value should be used throughout the module. By requiring it to be passed explicitly in later functions, we mitigate the risk of (in future versions) forgetting to pass the intended value, which otherwise could cause a silent error. I.e.:

def main(alpha=1):
    _sub1(alpha)

def _sub1(alpha):
    _sub2()  # Forgetting to pass alpha

def _sub2(alpha=1):
    print(alpha)

main(0)

[lostanlen]

ready to merge

[lostanlen]

@MuawizChaudhary merge ?