Create csr.py
There is a typo on line 334 which raises TypeError message
```
expected scalar, dense matrix/vector or csr matrixr
```
This corrects the typo to
```
expected scalar, dense matrix/vector or csr matrix
```
@@ -331,7 +331,7 @@ class csr_matrix(compressed._compressed_sparse_matrix):
other.sum_duplicates()
return multiply_by_csr(self, other)
else:
- msg = 'expected scalar, dense matrix/vector or csr matrixr'
+ msg = 'expected scalar, dense matrix/vector or csr matrix'
raise TypeError(msg)
# TODO(unno): Implement prune
