code: def quaternion_real(quaternion):
      """Return real part of quaternion.
  
      >>> quaternion_real([3, 0, 1, 2])
      3.0
  
      """
      return float(quaternion[0])
  
imports: import math
  import numpy
label_desc: Use image node_id 30 for calling a global function with example usage: quaternion_real(quaternion) and returns: float