Fix NameError: import missing Sum_coll in load_data.py

[Copilot]

load_data_Comp_1D_old and load_data_Comp_1D_new in spyrit/misc/load_data.py call Sum_coll, which is defined in spyrit/misc/matrix_tools.py but was never imported — causing a NameError at runtime.

Change

• spyrit/misc/load_data.py: Add missing import:

  from spyrit.misc.matrix_tools import Sum_coll

Original prompt

---

This section details on the original issue you should resolve

<issue_title>old code has undefined functions?</issue_title>
<issue_description>Some functions in spyrit.misc.load_data call an undefined function (Sum_coll), I'm guessing this is old code that was lost?

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes old code has undefined functions? #326

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