In the issue #72, we found that the implementation of CodeRefsTo() excludes all call type cross-references, which is inconsistent with the results of CodeRefsTo() in IDA Pro 7.0.

# a code xref is like a fallthrough or jump, not like a call.
for xref in idb.analysis.get_crefs_to(self.idb, ea,
     types=[idaapi.fl_JN, idaapi.fl_JF, idaapi.fl_F]):
     yield xref.frm

According to the comment, the developers excluded the calling flows. However, we found that the CodeRefsTo should include the calling flows according to an example in the idapython project (link). In the code, they use CodeRefsTo to find all callers of the target function. Thus, we modify the implementation of CodeRefsTo (also the CodeRefsFrom) to include the call flows.