Mass-composition

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Feature
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- Added to_simple method to Flowsheet. New test and example. (177)

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Feature
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- Improved prefix management on mc init from dataframe
- Added cleaning code to iron_ore_met_sample_data" method in sample_data
- No changes need to provide additional features to split_by_estimator since attr vars are already
passed to outputs of math operations. (172)

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Feature
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- Development to support the DAG with estimator example.
- Cleaned up the iron_ore_met_sample_data method in sample_data.
- Added estimation extra to pyproject.toml. (171)

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Bugfix
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- Fix for rogue edge creation in DAG.add_step method. (167)


Feature
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- DAGs using Stream operations can join more than 2 streams. see example 503_dag_with_partition. (168)

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Bugfix
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- Added missing name attribute on the output edges. (165)

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Bugfix
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- Fixed DAG incorrect edge successors using name lookup from graph. (163)