remove if clause blocking recalculation of conf_interval

[jagerber48]

Description

The check for self.ci_out is None blocks recalculation of confidence intervals in the event that they have already been calculated. But the "effort saving" technique is too blunt. If repeated calls to conf_interval are made with differing kwargs the results from the first calculation are unexpectedly returned every call. See Issue #791. The resolution is to continue caching the results into self.ci_out but to recalculate the results every time conf_interval is called. This shifts some "effort saving" responsibility out of lmfit to the user.

Type of Changes

• Bug fix
• New feature
• Refactoring / maintenance
• Documentation / examples

Tested on

Python: 3.9.13 (tags/v3.9.13:6de2ca5, May 17 2022, 16:36:42) [MSC v.1929 64 bit (AMD64)]

lmfit: 0.0.post2624+g1d011fc, scipy: 1.9.0, numpy: 1.23.1, asteval: 0.9.27, uncertainties: 3.1.7

Verification

Have you

• included docstrings that follow PEP 257?

• referenced existing Issue and/or provided relevant link to mailing list?

• verified that existing tests pass locally?

• verified that the documentation builds locally?

• squashed/minimized your commits and written descriptive commit messages?

• added or updated existing tests to cover the changes?
• updated the documentation and/or added an entry to the release notes (doc/whatsnew.rst)?
• added an example?

[jagerber48]

This is actually my first public github PR and the building, pytesting etc. is all new to me so I'm working over a little bit of a learning curve. Thanks for patience with me.

[newville]

@jagerber48 Great, thanks very much! I think this is sufficiently short and discussed that I will just merge.