Statement Classification Model

[haohangyan]

This PR implements a statement classification model that predicts whether a statement type is correct based on subject-object pair group information. The features include:

• the evidence count for the statement
• whether either agent belongs to a protein family/complex
• the proportion of the statement evidence count within the total evidence count of the subject-object pair group
• the number of sources supporting the statement
• whether an opposite statement type exists within the subject-object pair group
• the ratio between the evidence count of the statement type and its opposite statement type within the pair group
• the total evidence count within the subject-object pair group

This classification class provides the following functionality:

• predict_pair: predict results from subject and object agent names
• predict_from_rows: predict results from formatted statement rows
• predict_from_hashes: predict results from a list of statement hashes