Remove filter direction attributes

[kkappler]

• by definition multiply in freq domain by complex response to go from units_in to units_out
• remove channel response filter by dividing

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (d5d6891) 83.66% compared to head (d6e917e) 83.72%.

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Additional details and impacted files

```diff @@ Coverage Diff @@ ## fix_issue_173 #181 +/- ## ================================================= + Coverage 83.66% 83.72% +0.05% ================================================= Files 270 270 Lines 20072 20019 -53 ================================================= - Hits 16793 16760 -33 + Misses 3279 3259 -20 ``` | [Flag](https://app.codecov.io/gh/kujaku11/mt_metadata/pull/181/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JP) | Coverage Δ | | |---|---|---| | [tests](https://app.codecov.io/gh/kujaku11/mt_metadata/pull/181/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JP) | `83.72% <100.00%> (+0.05%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JP#carryforward-flags-in-the-pull-request-comment) to find out more.

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