class_docstr: A d-dimensional Bézier segment.
  
  Parameters
  ----------
  control_points : (N, d) array
      Location of the *N* control points.
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docstr: The polynomial coefficients of the Bézier curve.
  
  .. warning:: Follows opposite convention from `numpy.polyval`.
  
  Returns
  -------
  (n+1, d) array
      Coefficients after expanding in polynomial basis, where :math:`n`
      is the degree of the Bézier curve and :math:`d` its dimension.
      These are the numbers (:math:`C_j`) such that the curve can be
      written :math:`\sum_{j=0}^n C_j t^j`.
  
  Notes
  -----
  The coefficients are calculated as
  
  .. math::
  
      {n \choose j} \sum_{i=0}^j (-1)^{i+j} {j \choose i} P_i
  
  where :math:`P_i` are the control points of the curve.
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code: def polynomial_coefficients(self):
      r"""
      The polynomial coefficients of the Bézier curve.
  
      .. warning:: Follows opposite convention from `numpy.polyval`.
  
      Returns
      -------
      (n+1, d) array
          Coefficients after expanding in polynomial basis, where :math:`n`
          is the degree of the Bézier curve and :math:`d` its dimension.
          These are the numbers (:math:`C_j`) such that the curve can be
          written :math:`\sum_{j=0}^n C_j t^j`.
  
      Notes
      -----
      The coefficients are calculated as
  
      .. math::
  
          {n \choose j} \sum_{i=0}^j (-1)^{i+j} {j \choose i} P_i
  
      where :math:`P_i` are the control points of the curve.
      """
      n = self.degree
      # matplotlib uses n <= 4. overflow plausible starting around n = 15.
      if n > 10:
          warnings.warn(
              "Polynomial coefficients formula unstable for high "
              "order Bezier curves!",
              RuntimeWarning,
          )
      P = self.control_points
      j = np.arange(n + 1)[:, None]
      i = np.arange(n + 1)[None, :]  # _comb is non-zero for i <= j
      prefactor = (-1) ** (i + j) * _comb(
          j, i
      )  # j on axis 0, i on axis 1
      return _comb(n, j) * prefactor @ P
  
imports: from functools import lru_cache
  import math
  import warnings
  import numpy
  from matplotlib import _api
label_desc: Use image node_id 7 for calling the BezierSegment obj's underlying member method code with example usage: obj.polynomial_coefficients() and returns: unknown