Validate generated XML for charts, images and shapes.

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Removal vestigial schema URI

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Refactored SubElement creation for readability; one-liner a = x if y else z are awful to debug.

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support oneCellAnchor for images
split out anchor writer

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Already replaced by declarations in shared.ooxml

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Break conditional formatting into separate module.

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Reformatted imports - one line per import for multiline imports.

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Move safe_string to compatibility for easier reuse.
Add absolute imports to avoid confusion with generic module names.

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Remove unnecessary condition and import.

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Writers can depend upon self.root and don’t need to pass it around between methods.

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Updated setup

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Merge upstream

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use safe_string in write_anchor

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Merged in TWAC/openpyxl/1.8 (pull request #61)

support oneCellAnchor for images

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Corrected missing dependency.

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Corrected order of paramters.

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Optimisation although the function doesn’t appear to be in use.

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Markup some calls to serialise relations which need decoupling.
It should be either the Writer (Image, Chart, Shape) or the caller that serialises the relations or the worksheet writer or possibly a dedicated RelationWriter.

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Make class TYPES an immutable.
Refactor to make relations self representable.

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New style properties, make name checking regex class constant - doesn’t need recompling on each check.

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