class_docstr: Class to denote a base vector.
class_docstr_tok: ["Class","to","denote","a","base","vector","."]
code: def __new__(cls, index, system, pretty_str=None, latex_str=None):
      if pretty_str is None:
          pretty_str = "x{}".format(index)
      if latex_str is None:
          latex_str = "x_{}".format(index)
      pretty_str = str(pretty_str)
      latex_str = str(latex_str)
      # Verify arguments
      if index not in range(0, 3):
          raise ValueError("index must be 0, 1 or 2")
      if not isinstance(system, CoordSys3D):
          raise TypeError("system should be a CoordSys3D")
      name = system._vector_names[index]
      # Initialize an object
      obj = super().__new__(cls, S(index), system)
      # Assign important attributes
      obj._base_instance = obj
      obj._components = {obj: S.One}
      obj._measure_number = S.One
      obj._name = system._name + "." + name
      obj._pretty_form = "" + pretty_str
      obj._latex_form = latex_str
      obj._system = system
      # The _id is used for printing purposes
      obj._id = (index, system)
      assumptions = {"commutative": True}
      obj._assumptions = StdFactKB(assumptions)
  
      # This attr is used for re-expression to one of the systems
      # involved in the definition of the Vector. Applies to
      # VectorMul and VectorAdd too.
      obj._sys = system
  
      return obj
  
imports: from __future__ import annotations
  from itertools import product
  from sympy.core.add import Add
  from sympy.core.assumptions import StdFactKB
  from sympy.core.expr import AtomicExpr, Expr
  from sympy.core.power import Pow
  from sympy.core.singleton import S
  from sympy.core.sorting import default_sort_key
  from sympy.core.sympify import sympify
  from sympy.functions.elementary.miscellaneous import sqrt
  from sympy.matrices.immutable import ImmutableDenseMatrix
  from sympy.vector.basisdependent import BasisDependentZero, BasisDependent, BasisDependentMul, BasisDependentAdd
  from sympy.vector.coordsysrect import CoordSys3D
  from sympy.vector.dyadic import Dyadic, BaseDyadic, DyadicAdd
label_desc: Use image node_id 1 for calling the BaseVector obj's underlying member method code with example usage: obj.__new__(cls, index, system, pretty_str, latex_str) and returns: obj