code: def to_bipartite_matrix(A):
      
      m, n = A.shape
      return four_blocks(zeros(m, m), A, A.T, zeros(n, n))
docs: Returns the adjacency matrix of a bipartite graph whose biadjacency
      matrix is `A`.
  
      `A` must be a NumPy array.
  
      If `A` has **m** rows and **n** columns, then the returned matrix has **m +
      n** rows and columns.