<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def create_adjacency_matrix(self, weights=None, fmt='coo', triu=False, drop_zeros=False):
 r""" Generates a weighted adjacency matrix in the desired sparse format Parameters weights : array_like, optional An array containing the throat values to enter into the matrix (in graph theory these are known as the 'weights'). If the array is Nt-long, it implies that the matrix is symmetric, so the upper and lower triangular regions are mirror images. If it is 2*Nt-long then it is assumed that the first Nt elements are for the upper triangle, and the last Nt element are for the lower triangular. If omitted, ones are used to create a standard adjacency matrix representing connectivity only. fmt : string, optional The sparse storage format to return. Options are: **'coo'** : (default) This is the native format of OpenPNM data **'lil'** : Enables row-wise slice of the matrix **'csr'** : Favored by most linear algebra routines **'dok'** : Enables subscript access of locations triu : boolean (default is ``False``) If ``True``, the returned sparse matrix only contains the upper- triangular elements. This argument is ignored if the ``weights`` array is 2*Nt-long. drop_zeros : boolean (default is ``False``) If ``True``, applies the ``eliminate_zeros`` method of the sparse array to remove all zero locations. Returns ------- An adjacency matrix in the specified Scipy sparse format. Notes ----- The adjacency matrix is used by OpenPNM for finding the pores connected to a give pore or set of pores. Specifically, an adjacency matrix has Np rows and Np columns. Each row represents a pore, containing non-zero values at the locations corresponding to the indices of the pores connected to that pore. The ``weights`` argument indicates what value to place at each location, with the default being 1's to simply indicate connections. Another useful option is throat indices, such that the data values on each row indicate which throats are connected to the pore. Examples -------- """

        # Check if provided data is valid
        if weights is None:
            weights = sp.ones((self.Nt,), dtype=int)
        elif sp.shape(weights)[0] not in [self.Nt, 2*self.Nt, (self.Nt, 2)]:
            raise Exception('Received weights are of incorrect length')

        # Append row & col to each other, and data to itself
        conn = self['throat.conns']
        row = conn[:, 0]
        col = conn[:, 1]
        if weights.shape == (2*self.Nt,):
            row = sp.append(row, conn[:, 1])
            col = sp.append(col, conn[:, 0])
        elif weights.shape == (self.Nt, 2):
            row = sp.append(row, conn[:, 1])
            col = sp.append(col, conn[:, 0])
            weights = weights.flatten(order='F')
        elif not triu:
            row = sp.append(row, conn[:, 1])
            col = sp.append(col, conn[:, 0])
            weights = sp.append(weights, weights)

        # Generate sparse adjacency matrix in 'coo' format
        temp = sprs.coo_matrix((weights, (row, col)), (self.Np, self.Np))

        if drop_zeros:
            temp.eliminate_zeros()

        # Convert to requested format
        if fmt == 'coo':
            pass  # temp is already in coo format
        elif fmt == 'csr':
            temp = temp.tocsr()
        elif fmt == 'lil':
            temp = temp.tolil()
        elif fmt == 'dok':
            temp = temp.todok()

        return temp