re-applied changes from…

re-applied changes from https://github.com/jskda/nltk/commit/06d75ceaec1c561d5d5548b597db6e6bb26eb0a3, cf https://github.com/nltk/nltk/issues/670

nltk/sem/relextract.py

@@ -112,7 +112,7 @@ def list2sym(lst):
     sym = sym.replace('.', '')
     return sym
 
-def _tree2semi_rel(tree):
+def tree2semi_rel(tree):
     """
     Group a chunk structure into a list of 'semi-relations' of the form (list(str), ``Tree``). 
 
@@ -143,7 +143,7 @@ def _tree2semi_rel(tree):
 
 def semi_rel2reldict(pairs, window=5, trace=False):
     """
-    Converts the pairs generated by ``_tree2semi_rel`` into a 'reldict': a dictionary which
+    Converts the pairs generated by ``tree2semi_rel`` into a 'reldict': a dictionary which
     stores information about the subject and object NEs plus the filler between them.
     Additionally, a left and right context of length =< window are captured (within
     a given input sentence).
@@ -211,9 +211,9 @@ def extract_rels(subjclass, objclass, doc, corpus='ace', pattern=None, window=10
             raise ValueError("your value for the object type has not been recognized: %s" % objclass)
         
     if corpus == 'ace' or corpus == 'conll2002':
-        pairs = _tree2semi_rel(doc)
+        pairs = tree2semi_rel(doc)
     elif corpus == 'ieer':
-        pairs = _tree2semi_rel(doc.text) + _tree2semi_rel(doc.headline)
+        pairs = tree2semi_rel(doc.text) + tree2semi_rel(doc.headline)
     else:
         raise ValueError("corpus type not recognized")
 

nltk/test/relextract.doctest

@@ -94,12 +94,12 @@ recognize pairs *(o, l)* of these kinds of entities such that *o* is
 located in *l*.
 
 The `sem.relextract` module provides some tools to help carry out a
-simple version of this task. The `_tree2semi_rel()` function splits a chunk
+simple version of this task. The `tree2semi_rel()` function splits a chunk
 document into a list of two-member lists, each of which consists of a
 (possibly empty) string followed by a `Tree` (i.e., a Named Entity):
 
     >>> from nltk.sem import relextract
-    >>> pairs = relextract._tree2semi_rel(tree)
+    >>> pairs = relextract.tree2semi_rel(tree)
     >>> for s, tree in pairs[18:22]:
     ...     print('("...%s", %s)' % (" ".join(s[-5:]),tree))
     ("...about first-level questions,'' said Ms.", (PERSON Cohn))