Extend causal identifier init (#996)

* Update __init__.py

initializer now gives access to construct estimand functions

Signed-off-by: Rose De Sicilia <[email protected]>

* fixed formatting issue

Signed-off-by: Amit Sharma <[email protected]>

---------

Signed-off-by: Rose De Sicilia <[email protected]>
Signed-off-by: Amit Sharma <[email protected]>
Co-authored-by: Amit Sharma <[email protected]>

Author: RoseDeSicilia26

dowhy/causal_identifier/__init__.py

@@ -2,6 +2,9 @@
     AutoIdentifier,
     BackdoorAdjustment,
     EstimandType,
+    construct_backdoor_estimand,
+    construct_frontdoor_estimand,
+    construct_iv_estimand,
     identify_effect_auto,
 )
 from dowhy.causal_identifier.id_identifier import IDIdentifier, identify_effect_id
@@ -17,4 +20,7 @@
     "IdentifiedEstimand",
     "IDIdentifier",
     "identify_effect",
+    "construct_backdoor_estimand",
+    "construct_frontdoor_estimand",
+    "construct_iv_estimand",
 ]