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Commit 2022-05-02 13:45 52a454af

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feat(category_theory/limits): pushouts and pullbacks in the opposite category (#13495) This PR adds duality isomorphisms for the categories wide_pushout_shape, wide_pullback_shape, walking_span, walking_cospan and produce pullbacks/pushouts in the opposite category when pushouts/pullbacks exist.

Estimated changes

Modified src/category_theory/limits/opposites.lean

added theorem category_theory.limits.has_pullbacks_opposite

added theorem category_theory.limits.has_pushouts_opposite

Modified src/category_theory/limits/shapes/pullbacks.lean

added def category_theory.limits.walking_cospan_op_equiv

added def category_theory.limits.walking_span_op_equiv

Modified src/category_theory/limits/shapes/wide_pullbacks.lean

added def category_theory.limits.wide_pullback_shape_op

added def category_theory.limits.wide_pullback_shape_op_equiv

added def category_theory.limits.wide_pullback_shape_op_map

added def category_theory.limits.wide_pullback_shape_op_unop

added def category_theory.limits.wide_pullback_shape_unop

added def category_theory.limits.wide_pullback_shape_unop_op

added def category_theory.limits.wide_pushout_shape_op

added def category_theory.limits.wide_pushout_shape_op_equiv

added def category_theory.limits.wide_pushout_shape_op_map

added def category_theory.limits.wide_pushout_shape_op_unop

added def category_theory.limits.wide_pushout_shape_unop

added def category_theory.limits.wide_pushout_shape_unop_op