def to_dense(tensor):
"""Converts a sparse tensor into a dense tensor and returns it.
# Arguments
tensor: A tensor instance (potentially sparse).
# Returns
A dense tensor.
# Examples
```python
>>> from keras import backend as K
>>> b = K.placeholder((2, 2), sparse=True)
>>> print(K.is_sparse(b))
True
>>> c = K.to_dense(b)
>>> print(K.is_sparse(c))
False
"""
if is_sparse(tensor):
return tf.sparse_tensor_to_dense(tensor)
else:
return tensor```
