Array in 1-dimension erro

[preetida]

Hi,
I am getting this error while adding a new column for MT genes.
What is that I am doing wrong?

adata = sc.read_10x_h5(dir_path + 'filtered_feature_bc_matrix.h5')
adata.var_names_make_unique() 
print(adata.X)
print(adata.obs['sample'].value_counts())
print(adata.obs['sample'].value_counts())
print(f'Number of cells before filter: {adata.n_obs}')

# Quality control - calculate QC covariates
adata.obs['n_counts'] = adata.X.sum(1)
adata.obs['log_counts'] = np.log(adata.obs['n_counts'])
adata.obs['n_genes'] = (adata.X > 0).sum(1)

mt_gene_mask = [gene.startswith('MT-') for gene in adata.var_names]
adata.obs['mt_frac'] = adata.X[:, mt_gene_mask].sum(1)/adata.obs['n_counts']

AV_24    571
Name: sample, dtype: int64
Number of cells before filter: 571
---------------------------------------------------------------------------
Exception                                 Traceback (most recent call last)
<ipython-input-26-5e7c1a502972> in <module>
     11 
     12 mt_gene_mask = [gene.startswith('MT-') for gene in adata.var_names]
---> 13 adata.obs['mt_frac'] = adata.X[:, mt_gene_mask].sum(1)/adata.obs['n_counts']

~/my_virtualenv/lib/python3.7/site-packages/pandas/core/series.py in __array_ufunc__(self, ufunc, method, *inputs, **kwargs)
    634         # for binary ops, use our custom dunder methods
    635         result = ops.maybe_dispatch_ufunc_to_dunder_op(
--> 636             self, ufunc, method, *inputs, **kwargs
    637         )
    638         if result is not NotImplemented:

pandas/_libs/ops_dispatch.pyx in pandas._libs.ops_dispatch.maybe_dispatch_ufunc_to_dunder_op()

~/my_virtualenv/lib/python3.7/site-packages/pandas/core/ops/common.py in new_method(self, other)
     62         other = item_from_zerodim(other)
     63 
---> 64         return method(self, other)
     65 
     66     return new_method

~/my_virtualenv/lib/python3.7/site-packages/pandas/core/ops/__init__.py in wrapper(left, right)
    503         result = arithmetic_op(lvalues, rvalues, op, str_rep)
    504 
--> 505         return _construct_result(left, result, index=left.index, name=res_name)
    506 
    507     wrapper.__name__ = op_name

~/my_virtualenv/lib/python3.7/site-packages/pandas/core/ops/__init__.py in _construct_result(left, result, index, name)
    476     # We do not pass dtype to ensure that the Series constructor
    477     #  does inference in the case where `result` has object-dtype.
--> 478     out = left._constructor(result, index=index)
    479     out = out.__finalize__(left)
    480 

~/my_virtualenv/lib/python3.7/site-packages/pandas/core/series.py in __init__(self, data, index, dtype, name, copy, fastpath)
    303                     data = data.copy()
    304             else:
--> 305                 data = sanitize_array(data, index, dtype, copy, raise_cast_failure=True)
    306 
    307                 data = SingleBlockManager(data, index, fastpath=True)

~/my_virtualenv/lib/python3.7/site-packages/pandas/core/construction.py in sanitize_array(data, index, dtype, copy, raise_cast_failure)
    480     elif subarr.ndim > 1:
    481         if isinstance(data, np.ndarray):
--> 482             raise Exception("Data must be 1-dimensional")
    483         else:
    484             subarr = com.asarray_tuplesafe(data, dtype=dtype)

Exception: Data must be 1-dimensional