code: def make_csr(A):
      
      # Convert to CSR or BSR if necessary
      if not (isspmatrix_csr(A) or isspmatrix_bsr(A)):
          try:
              A = csr_matrix(A)
              print('Implicit conversion of A to CSR in pyamg.blackbox.make_csr')
          except BaseException:
              raise TypeError('Argument A must have type csr_matrix or\
                      bsr_matrix, or be convertible to csr_matrix')
  
      if A.shape[0] != A.shape[1]:
          raise TypeError('Argument A must be a square')
  
      A = A.asfptype()
  
      return A
docs: Convert A to CSR, if A is not a CSR or BSR matrix already.
  
      Parameters
      ----------
      A : array, matrix, sparse matrix
          (n x n) matrix to convert to CSR
  
      Returns
      -------
      A : csr_matrix, bsr_matrix
          If A is csr_matrix or bsr_matrix, then do nothing and return A.
          Else, convert A to CSR if possible and return.
  
      Examples
      --------
      >>> from pyamg.gallery import poisson
      >>> from pyamg.blackbox import make_csr
      >>> A = poisson((40,40),format='csc')
      >>> Acsr = make_csr(A)
      Implicit conversion of A to CSR in pyamg.blackbox.make_csr