Minor edits on docstring

Author: szhan

python/tests/beagle_numba.py

@@ -367,11 +367,13 @@ def compute_forward_matrix(ref_h, query_h, trans_probs, mismatch_probs):
 @njit
 def compute_backward_matrix(ref_h, query_h, trans_probs, mismatch_probs):
     """
-    Implement backward algorithm to compute a backward probablity matrix of size (m, h).
+    Implement Li and Stephens backward algorithm.
 
     Reference haplotypes and query haplotype are subsetted to genotyped positions.
     So, they are a matrix of size (m, h) and an array of size m, respectively.
 
+    This computes a backward probablity matrix of size (m, h).
+
     In BEAGLE 4.1, the values are kept one position at a time. Here, we keep the values
     at all the positions.