def num_obs_dm(d):
d = np.asarray(d, order='<STR_LIT:c>')<EOL>is_valid_dm(d, tol=np.inf, throw=True, name='<STR_LIT:d>')<EOL>return d.shape[<NUM_LIT:0>]<EOL>
Returns the number of original observations that correspond to a
square, redundant distance matrix.

Parameters
----------
d : ndarray
    The target distance matrix.

Returns
-------
num_obs_dm : int
    The number of observations in the redundant distance matrix.