gparity()
========================================

.. py:function:: grassmanntn.param.gparity(canonical_index)

Returns the Grassmann parity of the canonical index.


**Parameters:**

- **canonical_index:** ``int``

  The composite index :math:`I` in the canonical encoder.

**Returns:**

- **out:** ``int``

  The summation :math:`p(I)` of the occupation numbers of individual bits.

Description
+++++++++++

Convert the composite index into the binary representation; i.e., an array of 0 and 1, then return the sum of this array. Namely, for :math:`I=(i_1,\cdots,i_n)`, :math:`p(I)` is defined by

.. math::

  p(I)\equiv\sum_{a=1}^n i_a