Adding Doubly Robust Estimation method (#1346)

* first commit

Signed-off-by: Nicholas Parente <[email protected]>

* rm small change

Signed-off-by: Nicholas Parente <[email protected]>

* example notebook

Signed-off-by: Nicholas Parente <[email protected]>

* nits

Signed-off-by: Nicholas Parente <[email protected]>

* tweak notebook

Signed-off-by: Nicholas Parente <[email protected]>

* rerun other notebook with symb

Signed-off-by: Nicholas Parente <[email protected]>

* more comments

Signed-off-by: Nicholas Parente <[email protected]>

* improvements

Signed-off-by: Nicholas Parente <[email protected]>

* tweak

Signed-off-by: Nicholas Parente <[email protected]>

* comments

Signed-off-by: Nicholas Parente <[email protected]>

* clip propensity scores

Signed-off-by: Nicholas Parente <[email protected]>

* add prop score clip arguments to docstring

Signed-off-by: Nicholas Parente <[email protected]>

* fix typo in docstring

Signed-off-by: Nicholas Parente <[email protected]>

* clear output cells

Signed-off-by: Nicholas Parente <[email protected]>

* backdoor

Signed-off-by: Nicholas Parente <[email protected]>

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Signed-off-by: Nicholas Parente <[email protected]>

Author: nparent1